
&+, 







VJ 





- **o« 










o ^ 





'" v<.L-,.V"V.--V-"''.^ ' 





^ ^"^ 




V 



f • o 





■0-r 











v 













^°- 



o_ * 




<*V> <V* * CBS * >£ \V 



0° 




















*>"** 



ELEMENTS 



OF 



ELECTRO-METALLURGY. 



BY ALFRED SMEE, F.R.S. 

if 

OiESL ACAD. NATURE CURIOSUM HON. SOC. 

1ENIOR-SURGEON TO THE ROYAL GENERAL DISPENSARY, 

* ALDERSGATE STREET; 

SURGEON TO THE BANK OF ENGLAND, TO THE CENTRAL LONDON 

OPHTHALMIC HOSPITAL; 

LATE LECTURER ON SURGERY, 

ETC. ETC. 

WITHDRAWN FROM W. 3. LlSSASYs 

FIRST AMERICAN, 

FROM THE THIRD LONDON EDITICLN. 

REVISED, CORRECTED, AND CONSIDERABLY ENLARGED. 
Illustrate ^ jgi th Electrotypes and numerous Woodcuts. 

Tfc to LC 

^V 2 2 1918 

NEW YORK: 
JOHN WILEY, 18 PARK PLACE. 

1852. 






c \ 



i a - I 



D 



C 



TO 

HIS ROYAL HIGHNESS 

THE PRINCE ALBERT, E.G. F.R.S. 

PRESIDENT OF THE SOCIETY OF ARTS, 
ETC. ETC. ETC. 

<Kf)i$ toork, 

DESIGNED TO EXTEND THE KNOWLEDGE OF SOME OF THOSE 
NUMEROUS ADAPTATIONS OF 

THE VAST FORCES OF ELECTRICITY TO THE WANTS OF MAN, 

THE FIRST SUCCESSFUL APPLICATIONS OF WHICH MUST EVER 
DISTINGUISH THE REIGN OF 

HER MAJESTY QUEEN VICTORIA, 

AS AN IMPORTANT ERA IN SCIENTIFIC HISTORY, • 

AND WHICH HAVE BESTOWED UPON THE ARTS AND MANUFACTURES 

A NEW POWER OF OPERATION, 



GRATEFULLY DEDICATED BY 



HIS ROYAL HIGHNESSES 



MOST OBEDIENT AND DUTIFUL SERVANT, 

ALFRED SMEE. 



KB 16 W» 



PREFACE 



This little work now appears before the public for the 
third time, and on each occasion the circumstances have 
materially differed. In the first instance, I should not 
have presumed to have undertaken the task, but for 
the pressing solicitations of many who were interested 
in the extension of those processes which have been 
here grouped together and desp:ri))jed under the general 
term of Electro-Metallurgy. When writing the first 
volume, I had barely entered the profession which it 
has fallen to my lot to follow, and consequently I had 
ample time at my disposal. By an intense application 
to the study of the precipitation of metals by means 
of experiments, this volume, however incomplete, was 
produced. 

The public, however, looked with so favourable an 
eye upon my earnest endeavours, that speedily a large 
impression of the work was sold, and the work was 
translated into the French, where it had even a more 
rapid sale. Upon this I extended my former experi- 



V1 PEEFACE. 



ments, and the second edition was issued. In the pro- 
secution of both these editions, I did not rely upon my 
•own experiments alone, but every manufactory was 
visited which I thought could furnish me with any 
facts which might aid me in composing the work ; and 
I cannot refrain from bearing testimony to the' very 
kind manner in which I have been universally received 
by every person whom I have had occasion to consult 
Throughout this work my readers cannot fail to 
observe that very many processes are detailed which 
are but very little described in other works. Perhaps 
it is only fair to mention, that many of these I have 
learnt during the exercise of my profession ; and, being 
perfectly independent of the subject, many processes 
have been freely shown to me for publication, which 
would not be communicated to an individual onl y seek- 
ing to extend his own business. 

^? f T^-T COnd editi ° n ' S ° lar S e a number ^s printed 
tnat I did not anticipate any further call. But the 
purchasers of the first were also found to be buyers of 
the second, and thus this edition had also a very large 
sale with the public. After a time, from causes to 
which I need not advert, the publisher sold the residue 
with my concurrence, by auction. From being pressed 

Sr, ffi i' f me ° f thG C ° pieS P ublished at ten 
shillings fetched but an inadequate amount. After 

a further time, however, the wants of the manu- 
facturer increased ; those copies, and the very same 
books which had been sold at a very low rate, readily 
fetched sixteen shillings, one guinea, and, in some 
instances, two guineas ; very curiously showing the 



PREFACE. Vll 

importance of adapting the supply of any commodity 
to the demand. 

At length it was determined to publish a third 
edition. In reviewing my former experiments, I saw 
that in many directions there was abundant scope for 
investigation. From my present occupations, however, 
I did not feel justified in following those alluring paths, 
and I have been compelled to content myself with adding 
to this edition some account of the processes and ex- 
periments which have been carried on by others : from 
this source alone this work has been increased about one 
sixth in bulk. Throughout all the editions, it has been 
my aim to write from my own knowledge, and therefore, 
unless the text expresses to the contrary, I have actu- 
ally witnessed the processes which have been detailed. 

The first and second editions held out prospective 
advantages to the manufacturer ; the present enables 
us to take a review of that which Electro-Metallurgy 
has absolutely effected. In the former editions, the 
economical relations of the subject were so carefully 
considered, that it has given me great pleasure to 
find that the stimulus of remuneration has been so 
effective that Electro-Metallurgy in no way falls short 
of the sanguine expectations then formed of it, but, on 
the contrary, has actually advanced in more extended 
spheres of operation. 

In presenting this third edition to the public, I can 
only regret that it is not more complete ; and I can 
assure the ardent investigator that much remains to be 
done ; that there are imtrodden paths of great promise 
to be explored, both as regards the production of elec- 



Vlll PREFACE. 

tricity, the source of power, and the application of that 
force to various processes. Electricity is but yet a new 
agent for the arts and manufactures, and, doubtless, 
generations unborn will regard with interest this cen- 
tury, in which it has been first applied to the wants of 
mankind. 

7, Finsbury Circus, 
Feb. 18th, 1351. 



CONTENTS, 



BOOK THE FIRST. 

OX GALVANISM. 

CHAP. I. 

ON GALVANIC BATTERIES. 

Electricity ; various kinds, 1—8. Voltaic Batteries ; circumstances ad- 
vantageous or disadvantageous to, 5—13. Proximate cause of Gal- 
vanism, 14—18. Resistance, Ohm's Formula, 18— 24. Different 
forms of Batteries, Couronne des Tasses, Wollaston, etc., 24—31. Ad- 
hesion of the hydrogen to the negative plate ; amalgamation of the 
positive, 34. Daniel? s Battery, 37— 44. Grove's Battery, <fcc 45—47. 
Smee's Battery, Odds and Ends Battery, 48—55. Comparison between 
the three batteries, 56—58 Pa £ e l 

CHAP. H. 

ON THE PROPERTIES OF GALVANIC BATTERIES, 

Sgma of a battery in action, 59. Harris's galvanometer, 60. Spark, 61. 
Voltaic electricity charges in Leyden jar, 62, Physiological effects, 63. 
Magnetism, 64—68. Galvanometers, 68—70. Horse-shoe temporary 
magnet, 71—73. Decomposition cell, voltameters, poles, 74—84. 
Laws of voltaic decomposition, 85, 86. Table of chemical equiva- 
lents, 87. Fluidity necessary to decomposition, 88. Conduction of 
fluids associated with decomposition, 88—90. Intensity necessary for 
decompositions, 91. Electrolysis; electro-chemical decomposition, 
92—98. Darnell's theory, 99." State of the fluid during decomposi- 
tion, 100. Effect of heat upon fluids, 101. Curious induction, 102. 
Author's theory of veltaie electricity 103 . . ■ • 84 



CONTENTS. 



CHAP. III. 

ON ADDITIONAL SOURCES OF VOLTAIC POWER. 

On hydro, animal, and lightning-electricity, considered as a source of 
power, 104. Magneto-electricity, 105 p age 80 



BOOK THE SECOND. 

ON ELECTRO-METALLURGY. 

CHAP. I. 

ON THE APPARATUS TO BE EMPLOYED FOR THE REDUCTION 

OF THE METALS. 

The idea of electro-metallurgy, suggested by Daniell's battery, 106 The 
porous tube or single-cell apparatus, 106—1 1 2. Capillary tube appa- 
ratus, 113. Plaster apparatus, zinc, iron, and tin positive poles 114 
Compound battery apparatus, ] 15, 116. Single battery apparatus 117 
118. Precipitating trough, 119. Single-cell and battery conjoined' 
120. Mason's arrangement, 121. Management of the apparatus, 122 
123. Lines on the reduced metal, how to be avoided, 124. Adhesion 
and non-adhesion of the reduced metal to its mould, 1 25—128 Appa- 
rent adhesion, 128. Lateral growth of the reduced metal, 129. Rela- 
tive expense of various modes of the reduction of metals. . 86 

CHAP. II. 

ON SUBSTANCES CAPABLE OF RECEIVING THE METALLIC DEFOSIT. 

Substances on which the deposit may take place, 130—131. Metals 132 
—136. JSbn-conducting substances; Sealing Wax, White Wax,' 136 
—139. Absorbent substances, as Paper and Plaster of Paris- means 
of rendering them non-absorbent, 139-141. Gutta percha 141 
Means of copying non-conducting substances by metals; by Plumbago 
143—145. Comparison between the methods, 145. . n? 

CHAP. III. 

ON THE LAWS REGULATING THE REDUCTION OF THE METALS. 

Metals capable of being reduced by the voltaic fluid, 146. States in 
which they exist, 146-148. Law for the reduction of the metals as 



CONTENTS. XI 

a black powder, 148. Law for the reduction of the metals in crystals, 
149. Law for the reduction of the metals in the reguline state, 150. 
Cause of the reduction in these states, 151. Mode of producing them, 
153—159. Mode of obtaining the black powder, 159. The crystal- 
line state, 160. The reguline state, 161. The same results obtainable 
by the single-cell apparatus, 165. Time required for the deposition of 
the metals, 167 Pag* un 

CHAP. IV. 

ON THE REDUCTION OF THE METALS. 

Introduction. Formation of salts, Ac, 168. Reduction of Platinum, 169. 
Gold, 170. Palladium, 171. Iiidium, 172. Rhodium, 173. Os- 
mium, 174. Silver, 175. Nickel, 176. Copper, 177. Zinc, 178. 
Cadmium, 179. Iron, 180. Tin, 181. Lead, 182. Antimony, 183. 
Bismuth, 184. Uranium, 185. Arsenic, 186. Tungstic acid, 187. 
Cobalt, 188. Manganese, 189 I 65 

CHAP. V. 

ON THE REDUCTION AND ANALYSIS OF ALLOYS. 

Law for the completion of the voltaic circuit through various solutions, 
190. Table of relative facility of decomposition, 191. . 224 



. BOOK THE THIRD. 

ON ELECTRO-GILDING, SILVER-PLATING, ETC. 

General directions, 192, Electro-gilding, 193. The auro-cyanide of 
potassium, 194. Apparatus, 195. Copper-gilding, 196. Water- 
gilding, 197. Gilding by amalgamation, 198. Electro-platinating, 
electro-platinizing, 199. Electro-palladiating, 200. Electro-plating, 
201. Plating by other means than Electro-Metallurgy, 202, On coat- 
ing metals with nickel, 203. On coppering metallic substances, 204. 
On coppering non^metallic substances, 205. On coppering medal- 
lions, 206 ; fruit, vegetables, &c, 207 ; baskets, 208 ; earthenware, 209. 
On coating metals with iron, zinc ? <fec, 210, Conclusion, 211. . 229 



X " CONTENTS. 



BOOK THE FOURTH. 

ON VARIOUS APPLICATIONS OF THE REDUCTION OF METALS 

BY GALVANISM. 

CHAP. I. 
ON THE MULTIPLICATION OP COINS AND MEDALS. 

Value of Electro-Metallurgy for the numismatist, 212. Mode of obtain 
mg he mould 213. Directly by the voltaic current, 214 By Tad 
fusible metal, &c, 215. By non-conducting substance , 216. MeS 
duphcatesofgold,217. Silver medals, 21 8* Medals of plainum 219 
Copper m edal, 220. Precautions to be taken to prevent air-bSble!' 

ThtkntsT,? 13 , , be empl ° yed ' 222 - S ^ le - U -W«** 232 
Thickness of the metal, 224. Removal of the cast from the mould, 225 

7?r f 16 !^' T medak ' 226 - Value of Electro-Metallurgy for me- 
dalists, 227. On the modes of making perfect medals, 228 2 „. 

CHAP. II. 

ON COPYING SEALS, PLASTER CASTS, ETC. 

Value of a seal, 229. Process for copyiug a seal, 230. Copper moulds 
from plaster medallions, 231. Quality of the reduced copped 23^269 

CHAP. III. 

ON THE MULTIPLICATION OF BEASSES. 

Process for obtaining Duplicate Brasses, 233. . . 2 74 

CHAP. IV. 

ON MAEING DIES FEOM EMBOSSED SURFACES. 

On metallic reverses from raised surfaces by galvanic agency, 234 Pecu- 
liarities of dies made from paper, 235. 276 

CHAP. V. 

ON THE MANUFACTURE OF MOULDS FROM FRUITS, VEGETABLES, ETC 

On making moulds from vegetable substances, 236. Chantrey's method, 

277 



CONTENTS. Xlll 



CHAP. VI. 



ON THE APPLICATION OF ELECTRO-METALLURGY TO SCULPTURE, BAS- 
RELIEFS, AND OTHER PURPOSES. 

The mode the sculptor adopts to obtain a metallic cast, 238. On making 
a metallic cast by Electro-Metallurgy, 239. The texture of the copper, 
240. General remarks, 241. On the application of Electro-Metallurgy 
for goldsmiths, 242 ; for surgeons, &c, 243. . . . Page 279 



BOOK THE FIFTH. 

ON THE ELECTROTYPE. 

CHAP. I. 
ON THE MULTIPLICATION OF TYPE. 

The mode of printing books, 244. On stereotyping, 245. On Electro- 
typing the type, 246 289 

CHAP. II. 

ON THE MULTIPLICATION OF PLAIN COPPER PLATES. 

The preparation of plain copper plates, 247. The electrotype plates, 
248. Process for their manufacture, 249. Manipulation of the bat- 
tery, 250. Precipitating trough, 251. Temperature, 252. Positive 
pole, 253. Regulation of the texture of the copper, 254. Single-cell 
apparatus, 255. Time required for the process, 256. Removal of the 
plate, 257. Mode of preparing the plate for engravers, 258. Economy 
in the manufactory, 259. Expense of the plate, 260. . . 292 

CHAP. III. 

ON COPYING ENGRAVED COPPER-PLATES. 

Engraved copper-plates, 261. Design on the plates, 262. Various kinds 
of engraving, 263. Uses of engraved plates, 264 ; for the potteries, 
265 ; for calico printers, 266 . . 800 



XIV CONTENTS. 

CHAP IV. 

ON THE MULTIPLICATION OF STEEL PLATES. 

Process for making a copper plate from a steel one, 267. Perkins's appa- 
ratus, 268. Comparison between the two processes, 269. Page 310 

CHAP V. 

ON MULTIPLICATION OF WOOD-CUTS. 

Design on wood-cuts, 270. Process, 271. Conclusion, 272. . 314 

CHAP. VI. 

ON MULTIPLICATION OF THE DAGUERREOTYPE. 

Value of the Electro-Metallurgy for the daguerreotype, 273. Process 
for obtaining the duplicate, 274. 327 



BOOK THE SIXTH. 



ON GALVANIC ETCHING. 
Action on the positive pole, 275. Etching by nitric acid, 276. Faults 
in the biting, 277. Galvanic etching, 278. Accelerating circum- 
stances, 279. Advantages of galvanic etching, 280. Gradations of 
tint, 281. General remarks, 282. 330 



BOOK THE SEVENTH. 



ON ELECTRO-DISRUPTIVE ETCHING. 

Process and practical application of the disruptive discharge of the 
etching of steel, 281 337 



BOOK THE EIGHTH. 



ON VOLTAIC BLASTING. 

On blasting rocks or sunken vessels under water, 282. Electrical 
clocks, 283. Improper uses of electricity . . 339 



LIST OF WOOD-CUTS AM) ILLUSTRATIONS. 









Page 


1. Daniell's Battery . 


. 


19, 


2. Grove's Battery . 


. 


22 


3. Smee's Battery, compound six cell 


s ... 


27 


4. Ditto ditto, for. Electrotype 


. 


27 


5. Ditto ditto, Odds-and-Ends' 


. . . . 


28 


6. Galvanometer 


. ... . . 


39 


7. Y shaped decomposition tube 


. . 


42 


8. Faraday's Voltameter . 


. 


43 


9. Faraday's Voltameter . 




. 


43 


10. Diaphragm Apparatus . 




. 


43 


11. Diaphragm Apparatus . 




. 


44 


12. Battery Voltameter 




. 


47 


13. Induced Voltaic Current 




. . . 


59 


14. Diagram of single ditto 




. . . . . 


64 


15. Therino-Voltaic Circuit 




.... 


70 


16. .Compound Voltaic Current . 




.... 


72 


17. Incomplete ditto , 




. 


74 


18. Hydro-Electric Machine 




.... 


80 


19. Electro-Galvanic ditto 




. . . . 


82 


20. Magneto-Electric ditto 




. . . . • 


84 


21. Single-cell Electrotype Apparatus 


• 


89 


22. Ditto ditto, another form 


. . . . . 


90 


23. Ditto ditto 


. . . . . 


91 


24. Single Battery Apparatus, with V 


'ertical Trough 


99 


25. Compound Trough Apparatus 


. 


100 


26. Mason's Apparatus 




104 


27. Single Battery, with Horizontal F 


recipitating Trough . 


107 


28. Mode of making wax moulds 


»....• 


128 


29. Apparatus for forming electr 


o salt 


8 


167 



xn 



LIST OF WOOD-CUTS AND ILLUSTRATIONS. 



Page 

30. Apparatus for making the red ferro-cyanate of potash . 170 

31. Artificial Electric Eel . * . 171 

32. Reduction of platinum by Compound Odds-and-Ends' Battery 111 

33. Apparatus for the reduction of silver . . ' . . . 191 

34. Metallo-chrome apparatus . . .. . . . 217 

35. Burnishers for gilt articles . . . . . . 236 

36. Process for electro-coppering 248 

Specimen of Electrotyped Type • . 291 

37. Dog's Head, Electrotyped from Clichee . . . .315 

38. Electrotype from Thomson's Seasons 321 

39. Glyphograph for Bankers' Cheques 324 

40. Glyphographic Map, from Messrs. Blackie's Gazetteer . . 325 

41. Apparatus for blasting in mines 340 



HISTORY 



OF 



ELECTRO-METALLURGY. 



We have not to extend our inquiry into remote periods, to 
trace the history of the arts of working in metals by the gal- 
vanic fluid, for truly it may be said that this art belongs to 
our own time, and is a characteristic of the present age. 
Whilst, however, we pursue our investigations into the his- 
tory of the subject, we find that it has had by no means a 
sudden origin ; for, at different periods, various persons have, 
by degrees, worked out one fact after another, till the com- 
prehensive branch of science has been developed, of which 
this volume is but a brief epitome. Electro-Metallurgy may 
be said to have had its origin in the discovery of the constant 
battery by the late Professor Daniell, for in that instrument 
the copper is continually reduced upon the negative plate. 
In his first experiment, this distinguished author observed, 
on removing a piece of the reduced copper from a platina 
electrode, that scratches on the latter were copied with 
accuracy on the copper. In this experiment we have the 
electrotype ; but the author, in the first paper detailing his 
experiments, had devoted all his attention and centred all 
his energies to the construction of the battery itself, and this 
valuable fact attracted but little of his notice. My much- 
respscted teacher lives indeed no more, to his pupils, his 



XVlll HISTORY OF 



friends, or his family ; but he lives to all time, from the 
profound researches which led to the construction of his 
battery. It may be true that the particular form of battery 
itself is now but very seldom used ; but if that battery had 
not been invented, Electro-Metallurgy would doubtless not 
have been added even now to our range of sciences. The 
name of Daniell is always, in my mind, intimately connected 
with Electro-Metallurgy ; and probably the professor himself 
little thought of the important results which would accrue 
from the invention of the battery, when he first made it 
known to the public. 

It was but a short time after the discovery of this battery, 
that Mr. De la Eue experimented on its properties. In a 
paper printed in the Philosophical Magazine for 1836, after 
describing a peculiar form of battery wl ich he adopts, the 
following remarkable passage is found : " The copper plate is 
also covered with a coating of metallic copper, which is con- 
tinually being deposited ; and so perfect is the sheet of copper 
thus formed, that, being stripped off, it has the counterpart of 
every scratch of the plate on which it is deposited." This 
paper seems to have attracted very little attention ; and, 
what seems still more singular, the author, although well 
qualified from his scientific attainments to have applied these 
facts, never indicated any practical benefit to which this 
experiment might lead. 

In this state the subject remained till October, 1838, when 
Professor Jacobi first announced that he could employ the 
reduction of copper, by galvanic agency, for the purposes of 
the arts. His process was called galvano-plastic. Imme- 
diately upon his discovery being announced in this country 
in 1839, Mr. Spencer stated that he had executed some 
medals in copper, to which the public afterwards gave the 
name of electrotypes or voltatypes, or, what is better, electro- 
medallions. 

Now yrhat is the precise value of the discovery of these 



ELECTRO-METALLURGY. XIX 

productions over the facts already described ? — for we have 
seen that the reduction of the copper as a perfect plate, 
taking the exact form of the negative metal on which it was 
deposited, had been already noticed. Why, it is simply the 
idea of the application of these facts ; but that idea has been 
everything for Electro-Metallurgy. The only apparatus 
which Mr. Spencer employed was ? in fact, a simple Daniell's 
battery. He employed various metals for the reception of 
the precipitated metal, which, however, was nothing new ; 
but he does not seem to have succeeded with any non-con- 
ducting substances. He executed medals, and perhaps dupli- 
cate copper plates ; but he does not give any details, as to 
the different methods for the reduction of the copper in differ- 
ent states, neither did he succeed with the reduction of any 
other metal. However, to Mr. Spencer the British public 
are principally indebted for the idea of the electrotype ; and 
perhaps the idea, as far as relates to its application in Great 
Britain, originated entirely with himself. 

Mr. Spencer's first paper was printed in the Journal of 
the Polytechnic Institution of Liverpool, in 1839; but the 
author complains that, by mismanagement, it was prevented 
from being read at the British Association. Any discourage- 
ment of science in the present time is greatly to be lamented, 
and the more especially when we see that the Germans are 
already taking the lead, not only in chemistry, but also in 
physiology. Every well-wisher of science must hope that 
an over-anxiety to prevent the publication of what is old, 
will not cause the referees of our learned societies to omit 
what is new. However, we are not so much behind-hand, 
but that a little zeal on the part of those who have an estab- 
lished reputation for scientific acquirements, joined to the 
effect which encouragement would have on the junior mem- 
bers of the country, will enable the British to keep the fore- 
most rank in science among the European nations. There 
are many now working zealously and ardently for the sake 



XX HISTORY OF 

of obtaining truth, struggling against the most disheartening 
opposition : let that opposition be changed to assistance, and 
great indeed will be the results. 

It is improper to throw the whole blame of the rejection 
of that paper upon Dr. Lardner, for this is by no means the 
only essay of importance which has been consigned to obli- 
vion. The rejection of valuable papers is a fault of the 
system, not of the man. At all the learned societies a paper 
submitted to the society is referred to persons to report upon 
its merits, and upon that report the committees act with 
regard to its publication or suppression, which, in some cases, 
is facetiously termed a careful deposit in the archives of the 
society, which expression literally means, that it is placed in 
some large box from which it will be excluded from the 
cheering influences of the sun's rays for ever. The exami- 
nation into the merits of any particular paper is, however, a 
most unthankful, disagreeable, and troublesome office. And 
it is not, therefore, surprising that the referees should some- 
times exercise their characters as men, in supporting their 
own or the opinions of their friends and those to whom they 
are under obligations, and occasionally forget their situation 
as judges. Their services being gratuitous, entitle the refe- 
rees to the heartiest thanks of the public ; but an important 
office like that they occupy, in which the prosperity of the 
whole country is interested, should decidedly not be held 
without remuneration, and when remunerated, the officers 
should be held responsible for their decisions. We perceive 
that had Jacobi not also been a discoverer of the electrotype, 
Electro-Metallurgy would not have added its valuable pro- 
cesses to the variety of arts which it comprises. Ponder 
this important matter, ye referees, carefully in your minds ! 
for you never can tell to what great end a single new fact or 
application, though in an ill-drawn up paper, may not ulti- 
mately tend. 

Perhaps in this place I may call the attention of scientific 



ELECTRO-METALLURGY. XXI 

men to the fact, that persons are actually employed by great 
Continental Powers to find out everything new that is dis- 
covered in this country, which, in a v^ry few hours, can be 
conveyed to any part of Europe. This hint is thrown out, 
not to deter Englishmen from generously giving their dis- 
coveries to all countries, but to cause them to be cautious 
not to mention their processes till they have appeared in 
some British publication, and thus vindicate the scientific 
character of our own country. This is the more necessary, 
as the English receive only the pleasure which the con- 
sciousness of being useful must afford, whilst the foreigner 
receives pecuniary emolument which singularly increases 
his desire of being acquainted with the inventions of other 
countries. 

I may further notice, in order to confirm what I have 
already stated, that the galvano-plastics of Jacobi, and the 
electrotype of Spencer, are not inventions the result of in- 
ductive reasoning and laborious research, like Professor 
Wheatstone's electro-telegraph or certain elaborate machines ; 
but merely an application of a fact, formerly known to 
Daniell, recorded particularly by De la Kue, and observed 
by hundreds of others ; that both Spencer and Jacobi could 
work only in copper, and in no other metal ; whilst, had 
they prosecuted their subject as a science, they would have 
seen that the same laws regulate the reduction of ail the 
metals. 

Electro-Metallurgy, as first made known to the world by 
Jacobi and Spencer, was the simplest of all inventions — the 
application of a fact known and recorded previously ; and 
it forms another instance of an invention of the greatest 
magnitude and utility to mankind, arising from most simple 
beginnings. 

The next discovery, which is fully equal in value to the 
idea of the electrotype itself, was made by Mr. Murray, 
He found out that non-conducting substances might have 



XXU HISTORY OF 

metallic copper thrown down upon them by previously 
applying black lead. Mr. Murray's process is extremely 
simple, and absolutely perfect. The first application of this 
invention was made in January, 1840 ; but it is to be 
lamented that he did not further extend its application and 
publish his researches, for his method was communicated 
orally, in the conversaziones of the Royal Institution, and 
not by any paper. I ]ay particular stress upon the value 
and perfection of plumbago, because some have denied its 
applicability : and the reader will find, throughout the 
whole of the work, that I have extended the use of this 
substance, to the benefit of the public and to the fame of the 
inventor. I have made very extensive inquiries, in order 
to ascertain who really first used plumbago for this purpose, 
and I have the testimony of several authorities that it was 
Mr. Murray, whose claim, therefore, to this invention is 
rendered quite indisputable. 

Since the above was written, I am happy to inform my 
readers that the Society of Arts thought fit to record their 
sense of the value of plumbago to Electro-Metallurgy by 
presenting Mr. Murray with a silver medal ; and perhaps 
the merit of Mr. Murray's discovery is much enhanced by 
black-lead not only answering its purpose most fully, but 
from being so simple that very few were likely to have 
thought of its application. I cannot conceive a more perfect 
substance than black-lead for this purpose, for the adhesion 
of hydrogen to it is so great that it would rather reduce a 
metallic salt than be evolved ; and this is the very property 
desirable for Electro-Metallurgy, and in this respect forms 
a striking contrast with the processes which had been pre- 
viously given by Mr. Solly, though, doubtless, had we not Mr. 
Murray's process, this would have formed a valuable addition 
to Electro-Metallurgy and have been universally adopted. 

Up to April, 1840, the single cell apparatus was invariably 
used, but then Mr. Mason very ingeniously devised another 



ELECTRO-METALLURGY. XX111 

mode by which the reduction might be effected. He used 
the single-cell apparatus as a Daniell's battery, which he 
connected with another cell to reduce another metal. In 
the second cell he used a copper positive electrode, which 
was dissolved during the action. By this means he made 
two metals by one pound of zinc, or, in other words, ob- 
tained two equivalents of copper for one of zinc. 

In the London Journal for April, 1840, as far as I know, 
is contained the first specimen of printing from an elec- 
trotype, by Newton. It is a small, rough sketch, but as 
the first of the kind is peculiarly interesting. 

The laws regulating the reduction of all metals in dif- 
ferent states, were first given in this work, as the re'sult of 
my own discoveries. By these we can throw down gold, 
silver, platinum, palladium, copper, iron, and almost all other 
metals in three states, namely, as a black powder, as a 
crystalline deposit, or as a flexible plate. These laws appear 
to me at once to raise the isolated facts known as the elec- 
trotype into a science, and to add Electro-Metallurgy as an 
auxiliary to the noble arts of this country. 

The regulation of the power of the battery to the strength 
of the metallic solution, also required an investigation of the 
principles which regulated the diffusion of the newly-formed 
salt, which is of great importance to the operator. In this 
work I have also appended data, whereby the manufacturer 
may calculate the expense of particular processes before he 
adopts them. The formulas for ascertaining the work that 
would be performed by a galvanic battery, under different 
circumstances, cannot fail to be of great utility to the work- 
man, if he rightly employ them ; and the intimate rationale 
of the motion of electricity in the battery must be a subject, 
at least, of great interest to all. The principle regulating 
the adhesion of the reduced metal is also one of permanent 
importance in all cases where it has to be removed from the 
plates on which it is deposited. 



XXIV HISTORY OF 

The number of experiments, I may even say the thou- 
sands, that have been tried to elucidate these laws (for this 
book is not a detail of experiments, but rather a digest of 
them), could never have been executed had I not first dis- 
covered my galvanic battery ; for its simplicity alone enabled 
me, without any assistance, to undergo the laborious under- 
taking. I am fully aware that some may disagree with me 
as to the superiority of my battery over all others for ex- 
perimental and manufacturing purposes. I shall not flinch 
upon this account from stating its advantages, especially as 
they appear to me likely to contribute to general benefit. 

The value of the battery process over all others, is its 
applicability to all classes ; moreover, when we use a single 
cell of the battery, the quantity of zinc dissolved to do any 
amount of work, is the same, or even less, than attends the 
use of the other apparatus ; because the local action in a 
battery of this construction is less than in the single-cell 
apparatus ; and, lastly, the quality of the precipitated metal 
can be regulated with the utmost nicety ; and I have no 
hesitation in stating, that the battery process is the only 
one that ever can be employed by the manufacturer with 
advantage. 

The platinized silver battery is peculiarly suitable for the 
operator, for when it is in action it communicates to him 
the degree of work that it is doing ; in fact, it completely 
talks to its possessor. If the current is very feeble, a faint 
murmur is heard ; if a little stronger, the battery whispers ; 
if a moderate current is passing, it hisses ; but if a violent 
one, it roars. At this present moment I have nineteen 
batteries at work in the same room where I am writing, and 
they are each telling me the work they are performing. 
This very instant the fall of a heavy ledger in a neighbour- 
ing office has jarred two wires into contact, and the roar 
of that one battery has immediately informed me of the fact 
notwithstanding the action of the eighteen others ; I have 



ELECTRO-METALLURGY. XXV 

separated the wires, and the universal singing communicates 
to me that all are now working satisfactorily. Any local 
action on the zinc in the same way is immediately notified 
by its different and peculiar voice, and I have been surprised 
how quickly the experimenter catches the characteristic 
peculiarity of each noise, which is learnt more readily than 
the sound of different bells in a strange house. 

With regard to the constancy of this battery, I may be 
expected to say a few words ; for, although theoretically it 
is not absolutely constant, yet, practically, for the purposes 
of the electro-metallurgist, its constancy remains for two or 
three days, or, in other words, until the battery is nearly 
exhausted ; and then, to replenish the solution of zinc with 
a fresh supply of dilute acid will not occupy more than half 
a minute. In recording my own experience of its practical, 
though not of its absolute, constancy, I can at the same time 
conjoin the testimony of some of the most extensive manufac- 
turers in this country. By the practical manufacturer this 
instrument is re-charged with acid, at intervals, varying 
from three days to a fortnight, or even a twelvemonth, ac- 
cording to the size of the vessel containing the acid. Whilst 
upon the use of the battery, I may state, that the platinum, 
with proper care, never wears off the silver, and that the 
platinized silver never undergoes the slightest change, or is 
affected by the slightest local action. 

The departments of Electro-Metallurgy comprising electro- 
gilding and plating, received great impulses from Elkington ; 
some of his processes being most admirable. As far as 
gilding is concerned, he was anticipated by Brugnatelli 
nearly forty years ago : the following passage has been 
pointed out to me by Mr. Brayley, then one of the editors 
of the Phil. Mag. "I have lately," adds he (Brugnatelli 
in a letter to Van Mons), "gilt in a complete manner two 
large silver medals, by bringing them into communication 
by means of a steel wire, with the negative pole of a voltaic 

2 



XXY1 HISTORY OF 

pile, and keeping them one after the other immersed in 
ammoniuret of gold, newly made and well saturated." This 
account is contained in the Phil. Mag. for 1805. but the 
same passage is also found in the " Archives of Philosophical 
Knowledge ;" but it is to be regretted that neither journal 
gave the letter or stated where it was published. This 
process differs in nothing from the ones now employed, and 
doubtless ought to be considered as the introduction of 
Electro-Metallurgy, being the first instance in which any 
metal was ever reduced by galvanism for the purposes of 
the arts. 

Since my last edition, the discovery of the use of the bi- 
sulphuret of carbon, for the deposition of bright silver 
and gold, is a very remarkable and important improvement 
of certain electro-metallurgic processes. In this discovery 
is contained the germ of other discoveries, which talented 
experimenters will not fail to turn to account. 

The processes for platinating, palladiating, &c, rest upon 
the authority of this work ; for hitherto the reduction of 
these metals, in any other state than that of the black 
powder, has been always considered impossible. The electro- 
metallurgist will be enabled, by the processes which he will 
find here fully described, to execute reliefs and intaglios in 
gold, and, in fact, in nearly every other metal ; facts alto- 
gether new in science. The working of all other metals, 
as in zinc, silver, &c. &c., except copper, is also due to 
the discovery of the laws regulating the precipitation of the 
metals. 

Every author has given directions for making moulds on 
plaster casts in metal ; but it is singular, that by no process 
hitherto known can a perfect reverse of plaster be obtained. 
In investigating the cause of this, I soon discovered that the 
extreme porosity of the plaster was the block over which 
they had all stumbled, and the difficulty was overcome by 
rendering the plaster non-absorbent. In this work the 



ELECTRO-METALLURGY. XXV11 



reader will find that the copying of reliefs in plaster is 
brought to the utmost possible perfection, and by very 
simple means. 

The success of this department of my experiments has 
amply repaid me for my labours and expense ; for there is 
not a town in England that I have happened to visit, and 
scarcely a street of this metropolis, where prepared plasters 
are not exposed to view for the purpose of alluring persons 
to follow the delightful recreation afforded by the practice of 
Electro-Metallurgy. 

The extended use of white-wax, bees'-wax, rosin, &c, for 
the electro-metallurgist, I trust will be found acceptable. 
Their manipulation I have given as the result of my own 
experience, and therefore, doubtless, those who make a 
trade of working these substances will find the account not 
so full as might have been expected or wished ; yet I believe 
practice alone is required to make the operator perfect in 
these arts. 

Since my last edition gutta percha has been added to the 
materials of the electro-metallurgist. I hardly know how I 
can adequately convey my sense of the immense importance 
of this new substance. Its plastic properties and its power 
of resisting acid and alkaline solutions render it of incalcu- 
lable value. For moulds it has already nearly superseded 
every other substance, so in like manner it has been em- 
ployed for troughs and other vessels : and Dr. Montgomerie, 
who first brought it into use in Great Britain, has earned 
for himself a lasting name amongst the benefactors of his 
country. Surely it would not be inconsistent to bestow a 
public reward upon those who render such important public 
services ! 

The application of Electro -Metallurgy to the copying of 
leaves, fruit, &c, is for the first time described in this work. 
The new mode of etching here detailed, I confidently trust, 
will be also found a valuable adjunct to the knowledge of 



XXV1U HISTORY OF 

the engraver. The principle which regulates the adhesion 
and non-adhesion of the plates will enable the operator to 
conduct his operations with certainty — a circumstance of no 
small importance to the engraver, ignorance on this score 
having already produced untoward results. 

In this history, a sketch only has been given of the 
leading discoveries ; but undoubtedly the person who carries 
out a new branch of science is deserving of considerable 
praise, for frequently he has to incur great expense without 
any immediate prospect of a return for his capital. 

The electrotype department of Electro-Metallurgy was, I 
believe, first undertaken as a business by Mr. Palmer ; who 
was speedily followed by De la Rue, and afterwards by 
Lockett, Mabley, and several others : though, not having 
seen the productions of the latter, I have been unable to 
report more minutely of their works. 

The laws which I have given in this work, and the univer- 
sality of their application, will doubtless influence importantly 
the attainment of the grand object of using the galvanic fluid 
commonly among our manufacturers ; and having thus, as I 
believe, raised the isolated facts called the Electrotype into a 
vast and comprehensive branch of science, a new name is re- 
quired which may be suitable to its importance, and embrace 
its various applications. The term which I have ventured to 
apply to the science is Electro-Metallurgy, which com- 
prises the principles regulating all the arts of Working- in 
Metals by the Galvanic force ; and the value of the 
new nomenclature is evident, when we consider that it takes 
in every mode by which it is possible to work metals, either 
by dissolving or precipitating them by the agency of the 
voltaic current. 

As a surgeon, I feel bound to pass my opinion upon the 
effect which an extensive application of Electro-Metallurgy 
would have on the health of the workman ; and in one word 
I may state, that I believe the mode of working in metals by 



ELECTRO-METALLURGY. XXIX 

the galvanic fluid is more wholesome, and attended with far 
less deleterious properties, than the methods now practised. 
The use of the salts of gold, silver, and platinum, is liable to 
discolour the fingers ; but the other salts have no particular 
effect. However, in passing the above decided opinion, 
strengthened as it is by watching the effects of the experiments 
on myself, and also from paying attention to the health of 
some who have reduced electrotype copper by the hundred- 
weight, I feel but little doubt, that, if the electro-metallurgist 
were several times in a day to leave his work with his fingers 
covered with metallic solutions, and take his meals without 
any ablution, and repeat this for a long time, the quantity of 
metal which he would thus draw insensibly into his system 
might be attended with inconvenience. Several of the pro- 
cesses here detailed, as those of gilding, &c., are likely most 
materially to benefit the health of the workman, as they 
supersede the use of pernicious mercurial fumes. 

Those conducting electro-metallurgical operations gene- 
rally fatten with their occupation, the minute quantities of 
sulphate of zinc and sulphuric acid which they imbibe im- 
proving the tone of their stomach, helping digestion, and 
strengthening the whole frame. The salts of copper have 
the same effects as those of zinc, but perhaps, upon the 
whole, must not be made quite so free with. I would warn 
my reader against too free and careless a use of the cyanides, 
believing that the simple inhalation of the vapour which they 
emit is very pernicious ; but with proper care no fear need 
be entertained, and, doubtless, upon the whole, Electro- 
Metallurgy is a great blessing to the workman. 

The Electro-Metallurgist who requires further informa- 
tion on galvanism, should consult the original papers of the 
various authors who have most contributed to a knowledge 
of the subject; but I would especially urge every person 
interested in any department of Electro-Metallurgy to buy 
and keep ready for reference Brande's Manual of Chemistry, 



XXX HISTORY OP 

one of the most extensive and general collections of chemical 
facts in the English language. The operator will find it 
indispensable if he attempt to leave the beaten track, and 
follow new paths. He may also possess Gmelin's Chemistry, 
which is an excellent compilation from the transactions of 
learned societies, and scientific and philosophical journals. 
It is, however, most deficient in processes published in mono- 
graphs. 

Since my last edition, Electricity is employed not only for 
the voltaic battery, but also for the magneto-electric machine. 
Now, when this work was first written many of my scientific 
friends thought that the title would have been better had it 
been termed Voltaic-Metallurgy ; and, in fact, the processes 
were described abroad as galvano-plastics. I dissented from 
this nomenclature, because it appeared to me that although at 
that time we could only carry on the processes by voltaic 
electricity, yet the time would arrive when electricity from 
other sources would also be employed. That time has 
arrived ; and the magneto-electric machine is now being 
extensively applied for electro-metallurgy, and thus my term 
has been fully justified. 

No person can now plead ignorance of Electro-Metallurgy 
as an excuse for not following it. There are such a variety 
of works upon the subject to suit every class of persons, 
from a penny up to three or four shillings, that certainly he 
must be enabled to purchase one according to his means. 
The best of them are generally written by workmen, who 
detail in their own language, the processes they are in the 
habit of using. Those works which are made up by abstract- 
ing a part from one author and part from another, generally 
lose force from the inconsistent whole that they present; 
though, doubtless, there is not a single treatise upon the sub- 
ject that might not be useful to the incipient operator, and 
from which some good might not be drawn. 

It has often been mentioned to me, and considered strange, 



ELECTROMETALLURGY. XXXI 

that the Societies whose business it is to superintend and 
cherish the rising arts and infant sciences, should not contain 
any single paper on the new science of Electro-Metallurgy, 
and that the student is compelled to obtain his knowledge 
from other sources. For the electrotype, he may possess 
Spencer's treatise on that subject, although the mode of 
proceeding detailed by him is very different from those which 
the laws I have developed require me to recommend. Jacobi 
has written a treatise, in German, on Galvano-Plastics, which 
has been translated by Sturgeon. These two books, from 
respect to their authors, every electro-metallurgist should not 
only possess, but value and carefully preserve, as the first 
dawn of this delightful science. The manufacturer would do 
well to consult the various eiectro-metallurgic patents, the 
titles of which are given in the Appendix of this work, and 
abstracts of many of which are printed in various magazines. 
The original papers upon electro-metallurgy have now become 
so numerous, that every periodical contains notices, of various 
degrees of value and novelty, in some portions of this 
extensive subject. The value of these excellent periodicals 
in making public new discoveries and fostering talent, which 
would otherwise be frequently crushed by the overwhelming 
weight of interested opinion, is here evident, and to th^ir 
spirited editors this country is daily owing increase of kn< > 
ledge, power, and wealth. 



ELEMENTS 



OF 



ELECTRO-METALLURGY. 



BOOK THE FIRST. 

ON GALVANISM. 
CHAPTER I. 

ON GALVANIC BATTERIES. 

Electricity ; various kinds, 1 — 8. Voltaic Batteries ; circumstances ad- 
vantageous or disadvantageous to, 5 — 13. Proximate cause of Gal- 
vanism, 14 — 18. Resistance, Ohm's Formula, 18 — 24. Different 
forms of Batteries, Couronne des Tasses, Wollaston, &c, 24 — 31. Ad- 
hesion of the hydrogen to the negative plate ; amalgamation of the 
positive, 34. Daniell's Battery, 37 — 44. Grove's Battery, <tc, 45 — 47. 
Smee's Battery, Odds and Ends Battery, 48 — 55. Comparison between 
the three batteries, 56 — 58. 

(1.) As physicists have arranged an extensive series of 
effects under the general term of Heat, so they have named 
another series Light, and a third they have called Electricity. 
We find, if we examine organised bodies, that all these 
principles are capable of being produced through the medium 
of living bodies, for nearly all animals have the power of 
evolving heat; many insects, moreover, can voluntarily 
emit light : and the property of producing electricity is well 



% VOLTAIC BATTERY. 

evinced in the terrible shock of the electric eel, as well as 
in that of some other creatures. We are indeed in the 
habit of talking of the Electric fluid, or the Galvanic fluid, 
but this in reality is nothing but a license of expression 
suitable to our finite and material notions. 

(2.) In my Sources of Physics I have more particularly 
considered the mutual relation of these forces, and they all 
appear to be so singularly and intimately connected with 
each other, that from any one the others may be eliminated. 
As a high generalisation we may assume that any new at- 
traction will produce force, and that this force may act upon 
attracted matter, and produce, according to circumstances, 
heat, light, galvanism or electricity. 

(3.) Electricity is the only force of which we have par- 
ticularly to treat in this work, and this subject is subdivided 
into several departments : as electricity of tension, or fric- 
tional electricity, where the effects of electricity derived 
from the electrifying machine are considered ; therino- or 
sterseo-electricity, where it is derived from solid bodies 
through the agency of heat ; animal electricity, from or- 
ganised bodies ; magnetic electricity, from the natural or 
artificial magnet; and voltaic or galvanic, where it is ob- 
tained from the voltaic pile. 

(4.) Although these names, from their multiplicity, may 
tend to confuse, be it remembered, there is but one elec- 
tricity which thus manifests itself in such different ways, 
either under varying circumstances, or from differences from 
whence it is derived. Our inquiry will not extend into all 
these details, but principally into its effects when obtained 
from the voltaic battery. 

(5.) The phenomena, to w r hich the name of voltaic or 
galvanic electricity has been given, are those which arise 
from the voltaic or galvanic battery, so named from its 
discoverers, Volta and Galvani. They found that two 
pieces of metal, possessing different facilities for combination 



CONDUCTORS OF ELECTRICITY. S 

with oxygen, produced, when properly united, singular con- 
vulsions in a dead frog ; and, following out this experiment, 
they constructed the battery, which has now, from the im- 
provements of later discoverers, become so powerful and 
valuable an instrument. 

(6.) Without pursuing in detail the interesting experi- 
ments of subsequent authors, it must always be borne in 
mind, that, to make a galvanic battery with advantage, two 
conducting substances must be employed, and a compound 
conducting fluid must intervene, capable of being decomposed, 
and the resulting t compound formed should be removed 
as rapidly as possible out of the sphere of its production by 
the solvent powers of the fluid. The first substance should 
have the strongest possible affinity for one element of the 
fluid, and the second substance the least possible affinity. 
Thus, in a simple circuit, composed of zinc, silver, and 
water (the water being rendered a good conductor by the 
addition of acid,) zinc has a very strong attraction for th© 
oxygen of the fluid, whilst silver has a very slight attraction ; 
and therefore a powerful current is generated. As a gal- 
vanic curiosity Becquerel has described a battery made by 
an acid and alkali, separated from each other by a porous 
diaphragm, and simply connected by a platinum wire. Mr. 
Grove has also described an interesting arrangement of 
nitric acid and muriatic acid, separated by a diaphragm and 
connected together by gold leaf immersed in both fluids. 
In this case oxygen is transferred over to the muriatic acid, 
chlorine is set free, and one piece of gold becomes dissolved. 
The older electricians considered that galvanic batteries 
might be made of muscle and brain, beet-root, and various 
other non-conducting substances, but probably their obser- 
vations were inaccurate.* 

(7.) With regard to the relative conducting powers of 

* The voltaic currents in the living animal have described in the 
Elements of Electro-Biology. 



4 ELECTRO-POSITIVE ELECTRO-NEGATIVE PLATES. 

bodies, the metals, and all the varieties of carbon excepting 
the diamond, hold the foremost rank among solids. The 
fluids are generally imperfect conductors ; none more so 
than pure water: though in combination with the acids, 
pure alkalies, or any of the salts, it forms a good conductor. 
Fused chlorides and iodides are also good conductors. The 
metals are conductors in the following order : silver, copper, 
lead, gold, brass, zinc, tin, platinum, palladium, and iron. 

(8.) If we except the earthy and alkaline metals, as 
potassium, sodium, &c, zinc has by far the strongest affinity 
for oxygen ; and on this account is invariably used as the 
electro-positive metal (the term applied to the metal which 
is acted upon by the solution, or which in reality acts on 
the fluid). All other metals, in any acid solution, are 
electro-negative to them ; the term used to imply the op- 
posite state to electro-positive. The following table shows 
the state of electricity in which the metals stand with regard 
to each other in acid solutions, where every metal is positive 
to all below it and negative to all above it. This series 
relates only to a dilute sulphuric acid solution, for it varies 
with almost every other solution used : — 

Potassium, Iron, Silver, 

Barium, Bismuth, Palladium, 

Zinc, Antimony, Gold, 

Cadmium, Lead, Charcoal, 

Tin, Copper, Platinum. 

This order appears to me to require to be again made the 
subject of experiment ; I would suggest that, for this in- 
vestigation, every metal should be used in a finely divided 
state, similar to the finely divided platinum of my battery. 

(9.) When a metal which acts slightly upon a fluid (as 
for instance, copper) is brought into contact with another 
metal, which has a stronger affinity for the oxygen of the 
fluid, the latter, or electro-positive, is dissolved, and gives a 



ELECTRO-NEGATIVE PLATES. 5 

negative tendency to the former, which in that state does 
not act at all upon the fluid, but is preserved by the latter. 
Of this singular property Sir H. Davy took advantage, for 
the protection of the copper sheathing of vessels, which was 
effectually preserved from decay by pieces of zinc or iron 
placed in contact with it under the water ; but then unfor- 
tunately the copper, ceasing to be deleterious, did not 
prevent the adhesion of marine animals and vegetables, 
which accumulated to such an extent as materially to impede 
the ship's progress through the water. In this way zinc 
protects ail the less oxidable metals, when pure ; but if the 
electro-negative metals be contaminated with charcoal, or 
with a metal having less affinity for oxygen, they will still 
be acted upon. This doctrine of negative tendencies appears 
to be much overrated, for a metal can only be protected by 
the negative tendency, when hydrogen has to be evolved 
from the metal to be protected; thus, zinc will protect 
copper when placed in dilute sulphuric or other saline 
solutions, but no voltaic force will protect the copper when 
placed in the salts of silver, gold, platinum, or palladium, or 
in nitrous acid, because the hydrogen in these cases is 
immediately absorbed, and the copper is acted upon by the 
liquid, or rather itself decomposes the fluid, by seizing upon 
the oxygen of the metallic salt. For the same reasons it 
is impossible to give a negative tendency to iron or tin, in a 
solution of sulphate of copper, because there is no hydrogen 
to protect the iron. There are a thousand other similar 
instances ; therefore let the electro-metallurgist place no 
reliance on giving a negative tendency to a metal, but take 
care in all his operations not to place one metal in a metallic 
solution which it is enabled to decompose. 

(JO.) The converse of this observation applies to the 
electro-positive metal, as the zinc ; for, when pure, it is not 
acted upon by the sulphuric acid till contact be made with 
some other metal having less affinity for oxygen ; if it con- 



O LOCAL ACTION, CHEMICAL THEORY. 

tain any electro-negative metal, however, it will not only be 
acted upon by the fluid for the generation of the galvanic 
current, but independently of this a great waste and expense 
will be incurred. This additional wasting is termed local 
action, and should be avoided in every possible way. 

(11.) Local action, arising as it does from either the zinc 
or the negative metal being contaminated with some other 
metal, is to be considered as an infinity of small batteries, the 
action of which is quite independent of the great battery ; 
where the hydrogen is entirely transferred to the negative 
plate, and where consequently no apparent action is visible 
at the positive plate. 

(12.) It is for this reason that the pure metals are exceed- 
ingly difficult to dissolve, particularly if the acids be also 
pure ; as, for instance, pure silver in pure diluted nitric 
acid, or pure zinc in dilute sulphuric acid ; because there is 
no local battery of different metals established to favour the 
solution. 

(13.) A battery, in an acid solution, when put into action, 
exhibits apparently no change at the electro-positive metal, 
or zinc, if the local action be destroyed ; although in fact it 
is the zinc which is being dissolved. On the contrary, the 
electro-negative metal, which is in reality undergoing no 
change, exhibits a copious disengagement of gas, which arises 
from the transference of the hydrogen to that plate, while 
the oxygen is all absorbed by the zinc. 

(14.) This leads us at once to the proximate cause of the 
voltaic current, for it is found that the amount of action on 
the zinc is exactly proportionate to the quantity of electricity 
produced ; hence zinc appears to be the fuel of the battery, 
holding the same place as coals in a fire. From these and 
various other facts, Dr. Wollaston, Dr. Faraday, and with 
them most of the present experimenters in this country, be- 
lieve that the chemical action of the acid solution on the 
zinc, or rather of the zinc on the water of the acid solution, 



CONTACT THEORY. RADIATION. 7 

is the source of the electric current in the voltaic battery ; 
and this is termed the Chemical Theory of the pile. The 
Germans again, and others, following Volta, believe that 
the chemical action is the effect of the electric current, and 
that the power is produced by the contact of two dissimilar 
metals ; and this latter has received the name of the Contact 
Theory. 

(15.) In opposition to the Contact Theory, Dr. Faraday 
has described, in the Philosophical Transactions, curious in- 
stances, where the connection of a single battery, excited by 
dilute sulphuric acid, was not made through any metal what- 
ever, but through a liquid capable of being decomposed by 
the stronger energies of the dilute sulphuric acid. He found 
that a solution of iodide of potassium was best adapted to 
show this interesting fact. 

(16.) Whichever theory be adopted, the use of the nega- 
tive metal is by no means apparent ; for the quantity of 
electricity developed, cceteris paribus, is exactly as the 
surface of negative metal exposed ; thus, provided there be 
no obstacle to overcome, if the surface of this be doubled, 
the quantity of electricity will be likewise doubled, The 
extent of surface of the positive metal, within certain limits, 
is not of so much consequence, although too great a deficiency 
of this is attended with detriment. The importance of the 

i surface of positive metal differs with every metal, and 
perhaps depends more on the attributes of the salt formed 
during the action of the battery. In a dilute acid solution, 
when zinc is used for the positive metal, the extent of sur- 
face is not very material ; but when other metals, as copper 
or iron, are employed in a decomposition apparatus, the 
size is of the utmost consequence, as we shall hereafter have 
particularly to notice. 

(17.) One circumstance must be noticed, that every point 

, of the negative offers a radiating point to the positive metal ; 

' for every point not so situated is much less active, and some- 



8 EXCITING FLUID OF GALVANIC BATTERIES. 

times even perfectly inactive. In different cases this pro- 
perty is shown more or less strikingly ; for if the hydrogen 
be removed in its nascent state, it will, under the combined 
action of its adhesion and elasticity, manifest itself at a great 
distance from the positive metal, and even quite without the 
sphere of its radiation, as is the case where the back of a 
piece of metal is active, while the front alone is opposite to 
the fluid. When very smooth metals are used, it will also 
pass to a great distance ; but w T hen a metal is prepared in the 
manner I have hereafter to point out, by platinum, the gas 
will only be given off from a small extent, though very vio- 
lently, when touched by the point of a fine zinc wire. In 
fact, the stratum of fluid interposed between the pieces of 
metals affords a great resistance to the galvanic fluid, and 
this is proportionate to the thickness of the stratum and its 
conducting power. 

(18.) A relation exists between the power, and the dis- 
tance interposed between the electro-positive and negative 
metals ; for, the nearer these can be brought together, the 
greater the quantity of electricity developed ; though the in- 
tensity is not influenced by the difference of arrangement. 

(19.) The function of the acid solution has already been 
partially explained ; for w r e have before mentioned that the 
water is decomposed, the hydrogen is transferred to the 
negative metal, and the oxygen combines with the zinc, and 
forms oxide of zinc. The acid now comes into play, and, in 
addition to its adding considerable conducting power to the 
solution, it removes the oxide to form the sulphate of zinc. 
The water which now remains undecomposed is required to 
dissolve the sulphate of zinc, for, as soon as the liquid 
becomes saturated with that salt, no farther galvanic action 
can take place, although the liquid may still remain intensely 
sour. This property is of great importance, because it shows 
us that the acid and water must be so regulated that the 
sulphate of zinc which results from the action may saturate 



QUANTITY AND INTENSITY. D 

the water and leave little or no excess of acid. Whatever 
acid is left beyond the saturation of the fluid by the sulphate 
of zinc, must of necessity be wasted, unless we dilute the 
solution with more water. It is a most striking experiment 
to add water to a battery charged with a saturated and acid 
solution of sulphate of zinc, as immediately activity and power 
are exhibited by that which appeared before to be inert and 
inoperative. The function of the water has been very much 
overlooked, or even altogether neglected; but for electro- 
metallurgical operations the fact must be continually borne 
in mind, and a sufficiency of fluid always added to the 
metallic salt, in order that when the salt is formed it may be 
freely dissolved. If the rivers had been filled with anhydrous 
sulphuric acid, and water had been manufactured in the 
laboratory, then we should have come to the conclusion that 
the water excited the battery, and the acid was of secondary 
importance ; but, as it has been the reverse, we have decided 
too carelessly that the acid excited the battery, and the water 
played a secondary part ; whereas the one is as necessary as 
the other, the acid to render soluble the metal, the water to 
dissolve the newly formed metallic salt. Different salts vary 
very much in the rapidity with which they are dissolved by 
fluids ; thus sulphate of zinc is very rapidly dissolved, 
ferrocyanate of potash and sulphate of copper very slowly, 
and this does not depend upon the quantity of salt the water 
will take up ; a^id there is no doubt that this property is of 
considerable importance, not only in the galvanic battery, but 
also in the precipitating trough. After these observations, 
we must not be deceived by imagining we can have a battery 
which will do much work, and at the same time take up but 
little space ; for any person may at once calculate the capa- 
bilities of a battery from its size, by first ascertaining the 
nature of the salt formed by the galvanic action, then its 
solubility in water, by which means we can learn to a nicety 
the utmost amount of galvanic power that can be attained 



10 QUANTITY OF ELECTRICITY IN DIFFERENT CASES. 

from any battery. The only chance we have of lessening 
the size of a galvanic battery, and at the same time per- 
forming the same work, is to take care that the salt made 
during the action of the battery should be soluble in but little 
water. 

(20.) Whatever exciting fluid is employed to charge the 
battery, its efficacy depends upon the same principles, but 
the intensity varies with each variation in the foreign body 
placed in the water ; thus dilute nitric acid, dilute sulphuric 
acid, or a solution of salt, all impart different powers to the 
battery : an increase, however, or diminution in the propor- 
tion of these, does not interfere with the intensity, though the 
quantity is materially altered ; for, if but ten drops of dilute 
sulphuric acid are placed in a gallon of water, the intensity 
would be the same as if a pint of acid were employed ; but 
the quantity in one case would be infinitely less than in the 
other. 

(21.) The nature of the exciting fluid also materially 
affects the resistance which is afforded to the galvanic current, 
for no two fluids, or no two strengths of fluids, conduct the 
galvanic power with equal facility. From the above con- 
siderations we arrive at the proper manner to make a galvanic 
battery ; first, we must have two good conducting substances, 
separated by a good conducting intervening liquid. The 
amount of action which it will produce will be proportionate 
to the ready action of the liquid on one substance, and its 
inaction on the other ; and will depend on the size of the 
terminal plates. This amount of action may be fairly called 
the power of the battery, but it is always lessened ; first, by 
a slight resistance which the metals afford to the passage of 
the current ; and secondly, by the resistance which the in- 
tervening liquid is sure to afford, which is proportionate to 
its thickness. If, instead of a good conducting metal, the 
connection between the terminal plates is made by any im- 
perfectly conducting substance, or any great length of wire, 



RESISTING MEDIUMS. OHM's FORMULA. 11 

then will also the power be still further materially lessened. 
A single cell, composed of two metals and an intervening 
fluid, provided it be large, is sufficient to produce any amount 
of action where no resistance is offered to the passage of 
the voltaic current. These will remain inactive while they 
do not touch; but as soon as contact takes place, either in 
the exciting fluid, at a distance, or through a fluid of more 
easy decomposition than the exciting fluid of the battery, the 
action immediately commences. The contact may be made 
through a great length of wire with the same result. In 
this case, however, if the wire be either long, of small dia- 
meter, or of a metal of no great conducting power, it will be 
seen that the hydrogen evolved from the negative metal will 
be materially lessened, showing that an obstacle is presented 
to the electric fluid, 

(22.) To overcome this obstacle we must have recourse 
to a number of galvanic batteries, arranged as a series ; that 
is, the zinc of one battery connected with the silver of the 
next, and this in regular continuation, leaving the extreme 
zinc and silver free. In this way a hundred batteries may 
be conjoined, but no more electricity is obtained ; for only the 
same amount of electricity passes as when one cell is used. 
Now, however, this same amount can pass through a much 
greater resistance, for it would seem as if, at every alternation 
of the battery, the electric fluid obtained a push to overcome 
any obstacle afforded to its passage. The amount of elec- 
tricity will have a pow r er of overcoming obstacles in a com- 
pound battery, equal to its power in a single cell, multiplied 
by the number of cells. By this arrangement the amount 
of electricity actually passing will not be increased beyond 
what it would have been, had there been no resistance to 
overcome. 

Ohm, in an elaborate and obscurely worded paper, has 
given a mathematical formula for the galvanic current. His 
general formula may be thus expressed. The action (A) is 



12 ohm's formula. 

equal to (the electromotive force (E) multiplied by the 
number of batteries) (n) divided (by the resistance the cur- 
rent has to overcome, external to the liquid of each battery 
(R) plus (the resistance encountered- by the peculiar ar- 
rangement of each cell r multiplied by the number of cells 

(n) ) )• 

It would be thus : — 

n E 

A= . 

nR+r 

In this formula he has discarded the terms quantity and 
intensity, and unfortunately has adopted the contact instead 
of the chemical theory of the pile, which is now universally 
held in England. 

(23.) There is no advantage, but even a loss, in using a 
battery with a series more than sufficient to nearly overcome 
a resistance, whether produced by a fluid to be decomposed, 
or by any other means ; for if ten cells arranged as a com- 
pound battery be sufficient to overcome the obstacle, the 
effect of sixty cells, arranged as six tens, would be nearly 
six times as much as if a single ten were used, because they 
would then form a battery of six times the size : but if the 
whole were used as one compound series, the resulting de- 
composition would be enormously less than six times the 
quantity, being but a trifle more than before ; and, to use a 
battery with advantage, this fact must be borne in mind. 
If, again, the surfaces be increased before sufficient series be 
obtained, in like manner it will not add a proportionate 
amount of power. The subjoined plans will illustrate the 
two modes of arranging a number of batteries, first, as one 
large battery, by connecting all the zincs and silvers 
together. 



C0UR0NNE DES TASSES. DE LUc's COLUMN, ETC. 13 

Or, secondly, into a compound battery by alternately con- 
necting jthe zinc of one battery with the silver of the second. 

— z — s z — s z — s z — s . 

(24.) A compound galvanic battery, or one of many cells, 
has the same quantity of electricity passing in each cell, and 
therefore the same quantity of zinc dissolved. On this ac- 
count, the fewer the cells that can be employed to overcome 
the obstacle, the greater will be the economy. It is obvious, 
therefore, that as soon as, by increasing the series or number 
of the cells, sufficient intensity has been attained to overcome 
partially the resistance, quantity should be sought by in- 
creasing the surface or size of the plates in each cell ; for 
when one cell, as a single series, requires one pound of zinc 
to do a given amount of work, when that same work is done 
more quickly by twelve cells, twelve pounds are dissolved — 
one pound in each cell ; and of whatever size the cells may 
be, still the result will be the same, for no more zinc will be 
dissolved. 

(25.) The simplest form of compound battery is the Cou- 
ronne des Tasses, which is composed of alternate slips of zinc 
and platinum soldered together ; the zinc is to be placed in 
one glass, the platinum in the next ; and the series, thus 
arranged, may be charged with dilute sulphuric acid : care 
must be taken that the metal of the alternate pairs does not 
touch in the fluid. 

(26.) When intensity alone is required, a large number of 
small plates should be used, as in De Luc's column, which is 
constructed of pairs of plates of dissimilar metals, separated 
by paper. There are several methods by which it may be 
made ; the most common of which is to place alternate discs 
of silvered paper on similar discs of zinc, taking care that 
the series (i.e. the relative position of zinc) has always the 
same direction. It may be also made of discs of silvered 
or gilt paper, the uncovered side having been first spread 



14 COMPOUND BATTERY, ETC. 

over with the black oxide of manganese and honey. How- 
ever, care must be taken that the manganese be not exposed 
to the sun, as in that case it is rendered inert ; and also that 
the silver or gilt paper be not covered with any varnish, as 
that which is usually sold in the shops : 500 to 1000 discs 
must be employed to make an efficient instrument. 

(27.) The larger batteries, which were in use for a number 
of years, consisted generally of copper and zinc, arranged in 
different forms, according to the fancy of the operator. 
Thus, the copper of each cell surrounded the zinc, and both 
were united to fit into a porcelain trough, with eight, ten, 
or more cells. Here each cell is to be considered as a dis- 
tinct battery, although the copper and zinc of the whole 
trough are united ; an arrangement contrived to remove the 
series of batteries from the trough at one time. 

(28.) In this compound battery a porcelain diaphragm 
separates each simple battery ; but Dr. Hare discovered that 
a series of batteries might be placed in one vessel, provided 
that the metals of each battery did not touch in the fluid, and 
that neither the electro-positive metal afforded a radiatory 
point to the electro-negative metal of any other but its own 
pair, nor that any electro-negative metal radiated in a 
similar manner to any electro-positive metal. This form of 
battery is very little known in this country, and I believe 
but seldom used anywhere. 

(29.) There is another form, which was devised by Cruik- 
shank, and which consists merely of square pieces of zinc 
and copper, soldered together, and fixed at regular intervals 
in a wooden trough ; the zinc always being in one direction. 
In this battery the metals themselves divide the cells. 

(30.) There are many other forms of compound batteries, 
which do not require particular mention, as the principles 
which have been already explained affect them all. 

(31.) Provided the metals be sufficient to carry the current, 
their thickness does not influence the quantity of electricity. 



THICKNESS OF METAL REQUIRED FOR A BATTERY. 15 

that depending upon the surface exposed to the fluid; but, 
if the metals be so thin that they cannot carry the electricity, 
a diminution in the quantity of the current produced will 
ensue, similar to that which arises from thin wires, simply 
because a resistance is afforded to the galvanic circuit. For 
this reason, earthenware coated with platinum was not found 
to answer for the negative plate of an acid battery, the 
platinum surface not being of sufficient thickness. Yet, 
however thin a metallic or good conducting surface be 
employed, the current will gradually traverse it ; a property 
of no small importance for the electrotype. 

(32.) As the metals are good conductors, and the metallic 
oxides non-conductors, it is important that the negative 
metal should expose a clean metallic surface, or else it will 
be perfectly inert ; therefore, when the old forms of batteries 
are employed, the copper should be thoroughly cleansed 
from oxide before the battery is put in action. 

(33.) When the metal is thoroughly cleaned before it is 
employed, it still very speedily, in fact, almost instan- 
taneously, loses its power. Now this depends principally, 
if not entirely, in a single battery, upon the hydrogen's 
adhering to the negative metal, which thereby becomes 
coated with a non-conducting surface of hydrogen, and is 
therefore rendered inoperative. The state of surface influ- 
ences this adhesive quality. 

The reader may readily convince himself of the truth of 
this. Let him immerse in a tumbler of dilute sulphuric acid 
a polished plate of copper, and then place a piece of zinc in 
contact with the copper below the surface of the fluid. 
Bubbles of hydrogen will speedily appear upon the surface 
of the copper, and will soon cover its entire surface. It 
will be seen that these bubbles, instead of rising to the 
surface, and escaping as soon as formed (or in other words 
being evolved), will continue adhering to the metal. This 
depends upon the principle called heterogeneous adhesion, 



16 ADHESION OF HYDROGEN TO METALLIC PLATES. 

which can only operate when the surfaces of bodies are 
brought into very close contact. A smooth surface of metal 
favours the adhesion of the gas to such an extent as to 
counterbalance the force with which it tends upwards to the 
surface of the fluid. This, considering the difference of 
specific gravity between hydrogen and water, can by no 
means be a trifling force. Mechanical roughening by sand 
paper obviates in some degree this annoyance, but is by no 
means entirely a remedy. The mode of overcoming this 
adhesion will be treated of when we describe my battery. 
To give an idea of the amount of hydrogen which will adhere 
to smooth metals, I have frequently seen platinum, the 
heaviest of all substances, rise, by the force of the hydrogen, 
to the top of the water, after it had been in contact with 
zinc. 

(34.) The same observations apply to the positive metal ; 
for, if even impure zinc be polished, the hydrogen will yet 
adhere to such an extent, that scarcely any action will take 
place till the surface is corroded, when it will immediately 
become violent. There is another mode, however, of over- 
coming this local action, which has been adverted to in this 
place, instead of mentioning it before, because I believe its 
action depends upon the facilitating the adhesion of hy- 
drogen ; this mode is the amalgamation of the zinc by mer- 
cury. In making a battery this should never be neglected, 
from its economy, as but a small quantity of mercury is 
required. It is effected by acting upon the surface of the 
zinc, either by acid, or by planing the oxidized surface and 
then rubbing it with metallic mercury. Practically, plates 
of zinc are placed for a short period in dilute sulphuric acid, 
when metallic mercury is well rubbed over them. In con- 
ducting this operation the workmen should be taught to 
endeavour to make the zinc absorb as much of the quick- 
silver as possible, and in the long run that will be found to 
be the most economical. Let us never forget to whom we 






AMALGAMATION OF THE POSITIVE METAL. 7 

owe this discovery, which of itself enables galvanic batteries 
to be used extensively in the arts. Ages to come will 
perhaps have to thank the inventor, whom we are too apt to 
forget because he was neither on the council of the Royal 
Society nor a London Professor, yet still the obligation from 
the public to Mr. Kemp is the same.* 

The explanation which I have ventured to give of this 
valuable improvement is the following : the mercury en- 
velopes the small portions of charcoal and foreign metals, 
and therefore the first gas evolved adheres so firmly to these, 
that every foreign point of metal becomes heated, so as to 
prevent farther action ; for, of all the metals known, there is 
none to which the hydrogen sticks so firmly as to mercury. 
A very instructive experiment proves that the absence of 
action depends on the adhesion of the hydrogen ; for, if 
mercury with zinc dissolved in it, be placed in dilute sul- 
phuric acid, it will give off no gas, but will be covered with 
large bubbles ; but if a little sulphate of copper, nitrate of 
silver, or nitro-muriate of platinum be placed in the acid, 
an instantaneous change ensues, for the hydrogen has not 
now to be evolved, but is absorbed in the nascent state, to 
reduce the oxides of these metals. The protective influence 
which mercury exerts upon zinc is only operative when the 
hydrogen has to be evolved and not absorbed ; thus it is but 
little protection to zinc when placed in dilute nitric acid, 
because the nascent hydrogen is absorbed by the nitrous acid, 
and does not infilm the zinc. This fact may be readily 
observed if two pieces of amalgamated zinc be taken of 
similar size ; when one is placed in dilute sulphuric acid, and 
the other in the dilute nitric, the degree of action upon the 
zinc will be found to be far greater in the latter than in the 

* Time only confirms the strong opinion which I entertain of the value 
of the discovery of the use of amalgamated zinc, and it was with satisfac- 
tion I read the above paragraph, copied into the obituary of Mr. Kemp, 
in the Gentleman's Magazine, as a proof that his biographer held the 
same opinion as myself. 

3 



18 AMALGAMATION OF THE POSITIVE METAL. 

former case. In fact, in dilute sulphuric acid, zinc well 
amalgamated will last for days, or even weeks, without 
suffering any important loss. These observations clearly 
indicate the necessity of abstaining altogether from the use 
of nitric acid, when w r e are desirous of obtaining the galvanic 
power at the lowest cost. 

(35.) In an elementary treatise it is unnecessary to en- 
large upon these views, but those desirous of entering into 
them can consult the Philosophical Magazine for April 1840, 
or the Transactions of the Society of Arts for that year. 
An observation of these facts led me to construct the Che- 
mico-mechanical battery, of which we shall speak after we 
have described the other forms. Before, however, entering 
upon that subject, there is still another property of metals 
which has not been adverted to : viz. that the least oxidable 
metals, as platinum, in common with the metals which have 
most affinity for oxygen, become coated, or so infilmed with 
air, that they are rendered useless, because they expose a 
film of badly conducting substance to the fluid instead of a 
metallic one. The film may be instantly destroyed by heat, 
or by strong nitric acid. This fact has been long known, 
and the familiar experiment of causing iron filings to swim, 
while magnesia, which is an impalpable powder, sinks, is an 
example. But I believe it had not been noticed as influ- 
encing galvanic effects till mentioned in the paper before 
quoted. 

(36.) The mode in which the hydrogen is evolved, is sup- 
posed to influence the power of the battery ; for, if removed 
from the negative metal in the nascent state by any sub- 
stance which readily yields oxygen to combine with it, this 
power is greater than when it is evolved. The cause of this 
is not exactly known ; some supposing that it arises from 
chemical action at both poles of the battery, whilst others 
explain it by supposing that the hydrogen carries off a 
certain portion of electricity of tension, as they find that a 



DANIELL S BATTERY, 



19 



gold leaf electrometer is affected when brought near the 
evolved hydrogen. 

(37.) No further improvement was made in the galvanic 
battery hitherto described ; all previous alterations being as 
to size or form, as flat cells, round cells ; or as to the ar- 
rangement of the metals, as to which should be innermost : 
but these can scarcely be called improvements. At length 
Professor Daniell turned his attention to the subject, and 
produced a battery on a principle altogether new. 

(38.) The form of battery which he recommended was 
from eight inches to two feet in height, and four inches in 
diameter. The outer vessel is to be made of copper, of 
which the external part may be painted, as it plays no part 
in generating electricity ; while the inner remains uncoated. 
Into this cylinder a solution of sulphate of copper is to be 
poured, instead of the dilute acid used in previous batteries ; 
but now, if a zinc plate were put into this solution, and 
contact were made, the copper of the solution w^ould be 
reduced upon the zinc as well as on the outer cylinder, and 
thus great waste would ensue. It therefore became neces- 
sary to enclose the zinc in a porous vessel, in order to sepa- 
rate it from the sulphate of copper. This was 
effected by a piece of the gullet of the ox ; and 
into this, which forms an inner vessel, the 
zinc, with dilute sulphuric acid, is to be placed. 
Thus we have an outer copper cylinder (c) 
with a solution of sulphate of copper (s), and 
an inner porous vessel (p) containing zinc (z) 
and dilute acid (a). As soon as contact is 
made, the zinc is dissolved, and sulphate of zinc 
is retained in the inner part of the vessel ; 
whilst, instead of the hydrogen being evolved 
at the negative metal, it reduces the copper 
from the sulphate of copper. The inner vessel 
must be looked upon as a disadvantage, because 



Fig.l, 




20 VARIOUS ARRANGEMENTS OF DANIELl's BATTERY. 

there is no doubt that it lessens the power of the battery by 
materially increasing the resistance. The more porous this 
vessel is, the greater is the quantity of electricity developed ; 
and so common brown paper, coarse canvass, and porous 
earthenware tubes are employed, instead of the bladder, or 
the lining membrane of the gullet or intestines, as formerly. 
Professor Daniell used for his positive metal cast zinc rods, 
which he amalgamated ; and, as a little copper always passes 
through the porous vessel, this should be repeated every 
time it is employed. The earthenware tubes immediately 
after use should be plunged into water, and there kept till 
all the sulphate of copper is dissolved out ; or else, by crys- 
tallization, it will sometimes disintegrate the vessel. 

(39.) Many have thought that the zinc being two inches 
apart from the copper is too far, and they have used cylin- 
ders which approach a great deal closer; but although 
there is no doubt that by these means increase of power is 
obtained by lessening the resistance, yet many more incon- 
veniences attend their application than the employment of 
the form originally suggested by Professor Daniell. In the 
use of porous tubes of every sort, whenever the reduction of 
a metal takes place, care must be taken that neither of the 
plates of the battery touch the porous vessel ; for otherwise 
the reduction of the metal will take place upon it, and at 
length a line of continuity will extend from one to the other. 
Candidates, ever anxious to obtain the fame of anew inven- 
tion, made this battery square, oblong, parallelopiped, and 
even in many other forms, without any real advantage ; for 
all the alterations, attended with benefits one way, have 
counterbalancing disadvantages. 

(40.) This battery has been thought to be principally 
valuable for its constant effects ; that is, for the power which 
it possesses of generating exactly the same amount of elec- 
tricity for a long time together. 

(41.) To obtain its constant effects, however, certain pre- 



CONSTANT EFFECTS OF DANIELL's BATTERY. 21 

cautions are required; for if we alter the resistance of any 
part of the voltaic circuit, whether in the cell of the battery 
or without it, the amount of electricity passing will vary : 
thus, if the size of the w^ires used for the communication be 
altered, or their length either materially' increased or dimi- 
nished, then will the quantity of electricity vary. The dis- 
tance between the poles, and also their size, must remain the 
same, and great care must be taken that the porous tubes 
be of the same texture ; for it is to be remembered, that if 
but one bad earthenware tube be used in a battery of 
large series, the quantity of electricity will be influenced 
throughout. 

(42.) Much misunderstanding has arisen from the use of 
the term constancy ; it is often thought to signify long-con- 
tinued action, whereas these properties are really different ; 
for a battery may be constant, but only remain in action for 
a short period ; and again, a battery might continue in action 
for years, and not be constant in its action : the property of 
long continuation, however, is by far the more valuable. 

(43.) The principal disadvantages of this battery are, first, 
the labour required to set it in action ; secondly, the trouble 
and expense attending the use of the porous tubes ; and 
further, the necessity of continually re-amalgamating the 
plates ; and, lastly, the small quantity of fluid which the 
porous pots contain to dissolve the sulphate of zinc. 

(44.) The essential advantage which this excellent battery 
possessed over all which preceded it, is the removal of the 
hydrogen, whilst in the nascent state, by its decomposing the 
sulphate of copper, instead of its evolution at the negative 
vessel. It is owing to this, also, that this battery gives off 
no fumes. To employ its decomposing effects on acidulated 
water, with platina poles, with the greatest advantage, a 
series of ten or twelve is required. 

(45.) Another battery, upon precisely the same principles? 
although applied in a very different way, was invented by 



22 



grove's battery. 




Mr. Grove. He uses, for his negative metal, plati- 
num (p), and in the inner porous cells he puts strong 
nitric acid (n), and in the outer vessel, with the 
zinc (z), dilute sulphuric or muriatic acid (a). The 
form which Mr. Grove prefers is a many-celled 
trough, like the Wollaston's, with flat parallelo- 
piped porous tubes in the interior ; and, as platinum 
is an expensive metal, he takes care that the whole 
surface is brought into full operation, by completely 
surrounding it with zinc. In this battery the nitric 
acid is decomposed by the hydrogen and deutoxide 
of nitrogen is evolved ; which, coming in contact 
with the atmospheric air, is converted into nitrous acid. 

(46.) This battery is remarkable for the intensity of its 
power ; a series of four being sufficient for most decompo- 
sitions. A large series exhibits the arc of light in a very 
brilliant manner ; for showing this phenomenon it exceeds 
all other batteries. This battery, however, with its great 
intensity, is not without some serious disadvantages ; for the 
nitrous fumes which are evolved during its action are ex- 
tremely pernicious to the animal economy, so much so that 
it is highly dangerous to be exposed to them without a free 
access of air. Many cases have come before myself of injury 
to the lungs, and even constitutional effects, from exposure 
to nitrous fumes ; and, therefore, in using this excellent 
battery, due precautions should be taken. These nitrous 
fumes will attack almost every metallic surface with which 
they come in contact, and therefore it should not be employed 
in a room where there are polished stoves or metallic appa- 
ratus. The nitrous acid moreover passes through the porous 
tubes, and attacks the zinc to a considerable extent, indepen- 
dently of that zinc which is dissolved to generate electricity ; 
and lastly, this battery has the objection of requiring porous 
tubes. 

(47.) We have thus seen that Mr. Grove's intense battery 



grove's battery. 23 

is, in its principle, similar to that proposed by Professor Daniell, 
for in both the hydrogen is removed by chemical means ; in 
the first instance by nitric acid, and in the second by sulphate 
of copper. It possesses a great advantage by having one of 
the best fluid conductors we are acquainted with ; for the 
nitrous acid formed during the action of the battery, has 
been found by Dr. Faraday to possess this valuable property 
in a most eminent degree. It is a curious fact that the use 
of nitric acid had long been known ; for in all the old forms 
of batteries, a certain proportion of this acid was employed 
in the charge. Of course there are many other modes by 
which the same results may be obtained ; as, for instance, 
by using nitrate of silver, or the salts of gold, palladium, and 
platinum, or by other oxygenated acids, as the iodic, chloric, 
and bromic. I have tried many other substances upon this 
principle, but have not arrived at any new result, nor have 
found any arrangement superior for its power to the nitric 
acid battery. 

A new substance, to be used in a similar manner, has lately 
been brought before the Chemical Society, a society which 
promises to give a great impetus to chemistry in this country. 
It is the dichromate of potassa, a solution of which is placed 
on the negative side of the battery, whilst dilute sulphuric 
acid is used on the zinc side. Now the zinc is dissolved on 
the outer side of the battery by the dilute sulphuric acid, and 
the dichromate is decomposed at the negative end ; by which 
means, as in all diaphragm batteries, you incur a double ex- 
pense without any advantage as to power, but with a slight 
sacrifice of space, and, in fact, by burning your candles at 
both ends. The ingenious application of this salt was first 
made known by Dr. Leeson.* Mr. Grove's battery, charged 

* A Daniell's battery, charged with dichromate of potassa, instead of 
sulphate of copper forms a Leeson's battery ; but it has never come into 
general use. 



24 THE CHEMICO-MECHANICAL BATTERY. 

with potash, instead of nitric acid, also forms a powerful 
instrument. 

A battery has been occasionally employed with iron for the 
negative pole. Shonbein showed that it might even be used 
as a Grove's battery ; but although means have been used to 
bring it into notoriety under a new name, it is not particu- 
larly employed, because the iron is liable to be acted upon. A 
platinized iron battery I have occasionally employed, but it 
is liable to the same objection. 

(48.) In conducting a series of experiments on the ferro- 
cyanuret of potassium, having had frequent occasion for the 
use of a galvanic battery, I found that although the two last 
were admirably contrived instruments, yet that it was very 
desirable to possess one that could be set in action at a mo- 
ment's notice, and with comparatively little trouble. It be- 
came thenceforth my endeavour to construct one that should 
require little or no labour in its employment, and this was 
followed by devising the Chemico-mechanical battery. 

(49.) This battery, after I had minutely investigated every 
property which belongs to the metals of which batteries are 
constructed, was made upon noticing the property which 
rough surfaces possess, of evolving the hydrogen, and smooth 
surfaces, of favouring its adhesion. Thus, whatever metal 
we use for our negative plate, we take care that it be rough- 
ened, either by a corrosive acid, as iron by sulphuric acid, 
copper and silver by nitric acid, or mechanically, by rubbing 
the surface with sand-paper. Even by these means the metals 
are rendered much more efficient ; but, to take advantage of 
this principle to the fullest extent, I cover platinum with 
finely divided black powder of platinum, by galvanic means ; 
that is, I place the platinum as the copper is placed in a 
Daniell's battery, but, instead of employing sulphate of copper 
in the outer vessel, I use a small quantity of nitro-muriate 
of platinum, so that the finely divided metal is thrown down 
on the sheet platinum previously roughened by sancl-paper. 



PRINCIPLE OF SMEE'S BATTERY. 25 

In this way it was also placed on palladium, silver (roughened 
by nitric acid), plated copper, iron of every sort, and on 
charcoal, with the same good result ; but no other metal was 
found to answer for its reception. The metal generally em- 
ployed is silver, because of its cheapness and its not under- 
going any alteration. But whatever metal be used, the 
principle is the same, viz. the affording a surface to which 
the hydrogen shall not adhere, but from which it shall be 
evolved ; and the infinity of the points which are presented 
by such a surface as above described, appears to be the cause 
of this excellent result. The preparation of the silver is now 
made a separate branch of a trade, and perhaps it is the first 
application of the decomposing power of the galvanic battery 
which was publicly sold. The platinized metal can now be 
bought ready for use ; but, for those who desire to perform 
this operation, a brief description is here added. 

(50.) The metal to be prepared should be of a thickness 
sufficient to carry the current of electricity, and should be 
roughened, either by sand-paper, as in the case of platinum 
or palladium, or, when silver is employed, by brushing it 
over with a little strong nitric acid, so that a frosted appear- 
ance is obtained. The silver is then washed, and placed in 
a vessel with dilute sulphuric acid, to which a few drops of 
nitro-muriate of platinum are added. A porous tube is then 
placed in this vessel, with a few drops of diluted sulphuric 
acid ; into this the zinc is put. Contact being made, the 
platinum will in a few seconds be thrown down upon the 
surface of the silver, as a black metallic powder. The opera- 
tion is now completed, and the platinized metal ready for 
use. However, iron, when thus prepared, is as effectual as 
silver, and may be sometimes employed with advantage. 
With this metal, all that is required is to rub a little nitro- 
muriate of platinum over it, and an immediate deposit of the 
black powder takes place. Palladium and iridium are found 
nearly as effectual as platinum to coat other metals with, and 

3* 



26 EXCITING FLUID. 

the platinized silver of commerce usually possesses a con- 
siderable quantity of this latter metal. Within the last few 
months an idea has prevailed in the minds of some, that 
wire gauze might be used with advantage ; but it is difficult 
to conceive where the benefit would lie, for the cost of the 
material would be greater, the surface for the same weight 
of metal would be less, and neither space nor power gained 
by its adoption. 

(51.) The liquid generally adopted to excite this battery 
is a mixture of one part by measure of sulphuric acid, and 
seven of water, which will be found amply strong for all 
purposes. Where we desire greater intensity, we can obtain 
it by the addition of a few drops of nitric acid ; but, if too 
much be used, it might attack the silver. When, however, 
platinized platina is employed, the nitric acid in very small 
quantities may be used with impunity. The electro-metal- 
lurgist will frequently find it advisable to use dilute sulphuric 
acid, only containing from 1-1 Oth to 1-1 6th of the pure acid, 
and adding some acid when the first is exhausted ; taking 
care, however, that the quantity of acid never exceed the 
l-4th of the original water, for any excess above that quantity 
will be useless, as the liquid will then become saturated with 
the sulphate of zinc (19). The zinc, acid, and water being 
severally required to excite the battery, it is possible to 
regulate them that they should all be exhausted at once, so 
that the zinc should neutralize the acid, and the resulting 
sulphate of zinc exactly saturate the water. This, however, 
is very interesting in principle, but practically it would be 
impossible to act with such precision ; yet we must never 
forget this fact whenever we charge our batteries. 

(52.) Numerous inquiries have been made as to what 
arrangement is best suited to this battery ; but this must 
depend upon the purpose for which it is employed. For the 
student's laboratory the porcelain or gutta percha trough 
of many cells appears to be best adapted ; and it is some- 



FORMS OF SMEK S BATTERY. 



27 



times so constructed, that any number of cells can be 
employed, independently of the others, as they may be 
required. The silver being the most expensive metal, the 
zinc should completely surround it, so that the whole of the 
silver maybe brought into action. Where a battery is 

Fig. 3. 




required to continue in action for a very long time, as for 
days or even weeks, a larger vessel, to contain more dilute 
acid, must be used : for electro-metallurgical purposes it has 
been hitherto found most economical to use a vessel of a size 
sufficient to hold liquid to last for seven or ten days. The 
form of battery now most universally employed for these 
purposes, consists of a piece of silver (s), on the top of 
which is fixed a beam of wood (w) to prevent contact with 
the silver. A binding screw is soldered on to the silver to 
Fig. 4. connect it to any required object. A strip 

of zinc, varying at the fancy of the operator 
(z) from one half to the entire width of the 
silver, is placed on each side of the wood, 
and both are held in their place by a bind- 
ing screw (6) sufficiently wide to embrace 
the zincs and wood. These batteries vary 
from the size of a tumbler to a ten or 
twelve gallon vessel. In the very ex- 
tensive application of this battery to the 
arts, the little pieces of zinc which remain 
undissolved in the battery form an im 




28 



FORMS OF SMEE S BATTERY. 



portant consideration to the manufacturer. Some distil the 
mercury from them, others sell them to the zinc works, 
whilst others have never turned them to any account at all, 
waiting patiently, in the hope that some more beneficial 
application of them might be discovered. These latter have 
hundred. weights of odds and ends in hand which they are 
desirous to employ. After considering the matter carefully, 
I have to propose the following use for them ; in fact, I 

make them the positive pole of a battery, 
by placing them at the bottom of a 
vessel and covering them with mercury. 
A silver wire is then placed down a 
glass or gutta percha tube into the 
quicksilver, so that the wire may no- 
where touch the dilute sulphuric acid, 
with which the vessel is filled, but simply 
make a good metallic communication 
with the mercurv. At the other end of 
the wire a binding screw may be at- 
tached for the convenience of the operator. The platinized 
silver plate (s) is then to be immersed in the fluid, and 
placed as near to the mercury as possible, without actually 
being in contact, whilst no part of it should be more than 
three inches from it, as a considerable reduction of power 
would then ensue. This form of battery may be fairly called 
the Odds and Ends Battery, and though not so philosophical 
an instrument in its construction as the form last described, 
yet no manufacturer should be without one to use up the 
scraps from his other batteries ; and I must say this instru- 
ment requires less trouble in its manipulation than any other 
form I have ever seen. An odds and ends compound 
battery, which will only require a binding screw at each end, 
may be made by placing the mercury and zinc at the bottom 
of a many-celled porcelain trough ; the platinized silver 
should be cut into suitable squares, leaving a narrow slip to 




FORMS OF SMEE's BATTERY. 20 

connect it with the next cell. The strip must be placed in 
a glass tube, or covered with any non-conducting substance, 
as gutta percha, leaving the end only to dip in the mercury 
of the next cell. A series* of little glasses may be used 
instead of the many celled trough for some purposes. The 
only objection which I have found in this form of compound 
battery, is the possibility of the zinc in one cell being com- 
pletely exhausted, when the silver wire will begin to dissolve ; 
in all other respects it is a delightful instrument when you 
do not care about obtaining the maximum of power, and you 
can obtain the galvanic principle by this means at a lower 
cost than by anv other way. The odds and ends batterv is 
admirably adapted for gilding and plating, or it may be em- 
ployed for any operation that requires much time for its 
performance. The charge for this battery might contain 
one-third by measure of strong sulphuric acid, as the local 
action is very trifling; but it is found more advisable not to 
employ the solution so strong, as, when nearly exhausted, 
the sulphate of zinc will sometimes envelope the zinc and 
mercury, and prevent farther action before the top part of 
the liquid is fully saturated. Some contrivance should 
be adopted to carry ofT the saturated liquid as soon as formed. 
An advantage of this instrument is, that spelter, or raw zinc, 
may be used instead of manufactured zinc, and that no mer- 
cury is wasted, as the whole is left after the solution of 
the zinc. 

(53.) When we desire to employ a battery for manufac- 
turing purposes, it might be as well in some cases to remove 
the sulphate of zinc as soon as formed, by means of a syphon 
tube passing to the bottom of the vessel, while fresh acid is 
continually supplied at the top ; but this is not generally 
necessary. For these purposes the battery should be so 
constructed, that any of the zinc plates, when worn out, can 
be readily replaced. There are many other forms which 



30 FORMS OF SMKe's BATTERY. 

may be adopted; as the circular, with the zinc outside ; or it 
may be used as a tumbler battery. 

(54.) The characteristic of this battery is the great quan- 
tity of electricity produced, and its simplicity ; moreover, it 
requires but very little trouble in its manipulation. The 
zinc seldom demands but one amalgamation, as that will 
generally last till the metal is all dissolved. It is very im- 
portant to use for batteries zinc as pure as possible, for by 
that means the chance of local action is materially lessened. 
The manufacturers of zinc plates have a trick which is very 
fatal to this metal, for they buy up the refuse or waste 
pieces which frequently contain solder, a composition of lead 
and tin, and melt them with the raw zinc. This mixture 
always tells its tale during the action of the battery, as a 
light spongy flocculent precipitate rises to the top of the 
liquid which is metallic tin, and when any particle touches 
the zinc a little local battery is formed, which causes great 
waste of metal. If the zinc or acid contains much tin it is 
almost hopeless to attempt any operation. 

(55.) In using this battery it is important that no salt of 
copper, lead, or other base metal be dropped into the exciting 
fluid, as by that means the silver would become coated 
therewith; the plain consequence being, that a surface of 
copper, instead of that of the finely divided platinum, is pre- 
sented to the fluid. From a want of knowledge of this fact, 
in some who have used the battery, I have seen the negative 
metal covered with copper, which finally becoming oxidated 
rendered the platinum useless. When this takes place, it is 
best removed by immersing the plate in dilute sulphuric 
acid, to which a few drops of nitro-muriate of platinum 
should be previously added ; by this process the baser metals 
are dissolved and metallic platinum thrown down. Some 
manufacturers prefer dipping the silver into a solution of 
this sort every week. In this battery the zinc is never re- 
duced upon the negative metal, from the sulphate of zinc 



COMPARISON BETWEEN THE THREE BATTERIES. 31 

formed during the action of the battery, so long as the ex- 
citing fluid contains any acid at all. Other interesting 
matter connected with this subject will be detailed when 
treating of the reduction of zinc. 

(56.) Such is a brief view of the three batteries now in 
use : Professor Daniell's excellent invention being distin- 
guished by its constancy ; Mr. Grove's powerful battery, by 
its intensity ; and my own by the cheapness with which the 
quantity of electricity may be developed, and by its sim- 
plicity. Neither of these can be regarded as a perfect 
galvanic battery, for each wants some of the properties of 
the others ; it is to be hoped, therefore, that e^ery attention 
will be given to the further improvement of these valuable 
instruments, until the good properties of each are combined 
in one. Which of the three is at present to be preferred, 
must depend upon the purpose for which it is required ; and 
the choice must of course be left to the operator. For my 
own part, it affords me much pleasure to see that the pla- 
tinized silver battery has fully answered the expectations 
which I formed of it ; or even, I may say, in its extensive 
application very far exceeded it, as the amount of work 
already actually performed by this instrument is much 
greater than the total amount done by all other batteries 
ever since their first invention. By some it has been too 
much extolled, by others too much blamed. Notwithstand- 
ing the mis-statements on both sides, it has fully stood the 
test of time, and has been employed by the public in a 
manner which I had not even hoped. The reason they 
prefer it for general and especially for heavy manufacturing 
purposes appears to be, that it does not require the use of 
porous tubes, nor of the strong acids, and that it does not 
give off poisonous fumes. It usually continues in active 
operation for six, eight, ten, or more days, when a sufficiency 
of acid is supplied to it. The zinc, as a rule, demands but 
one amalgamation after that operation has been thoroughly 



32 COMPARISON BETWEEN THE THREE BATTERIES. 



effected ; and the time required either for setting it in action 
or for maintaining its operation, is comparatively not worth 
a thought ; and, lastly, the expense of working it is reduced 
to the lowest possible amount, being exactly proportionate 
to the power obtained. With regard to the choice of the 
battery, it appear to me that he must be a clumsy operator 
who obtains the galvanic principle and cannot apply it; 
therefore the whole subject under consideration may be 
summed up by ascertaining with what battery the greatest 
amount of the galvanic fluid can be obtained at the smallest 
cost, the least labour, and the greatest convenience. These 
three batteries agree by being each excited by the action of 
zinc upon water, the formation of oxide of zinc, and its sub- 
sequent removal by the sulphuric acid forming a sulphate of 
zinc ; now, as this same salt is formed in each battery, the 
same quantity of water to dissolve the sulphate of zinc will 
be required to produce any amount of work, and therefore, 
whether Grove's, Daniell's, or my own battery be employed, 
the same sized vessel must be employed ; proving the fallacy 
of attempting to obtain a battery in a small compass where 
sulphate of zinc is formed. In Grove's and Daniell's battery, 
however, if the diaphragm be of a nature that precludes the 
free passage of the zinc to the side of the platinum or 
copper, then will the amount of action depend upon the 
capacity of the vessel in which the zinc is immediately 
placed, and in that case a much larger vessel will be re- 
quired for theirs than for mine. 

(57.) Perhaps I may be expected to give an approxima- 
tion to the relative cost of working the three batteries. In 
mine it is the cost of the zinc dissolved by the acid : zinc + 
acid + a local action. In the constant battery it is zinc + 
acid -f- sulphate of copper + much local action. Each cell of 
this, to do any given amount of work, would cost about 
twice as much as mine. In Grove's battery it is zinc + acid 
-fnitric acid reduced by the hydrogen+nitric acid combined 






THE THEME INEXHAUSTIBLE. 33 

with ammonia formed during the action of the battery -f 
extensive waste of the zinc= about three times as much as 
mine. 

(58.) The construction of all the various forms of galvanic 
batteries has now been considered, and the principles also on 
which the peculiarities of each are founded have been briefly 
explained ; though, if this important branch of our subject 
were to be alone discussed at a length proportionate to its 
value, this volume would not be sufficient for the interesting 
and important matter relating to it. 



u 



CHAP. II. 

ON THE PROPERTIES OF GALVANIC BATTERIES. 

Signs of a battery in action, 59. Harris's galvanometer, 60. Spark, 61. 
Yoltaic electricity charges in Ley den jar, 62. Physiological effects, 63. 
Magnetism, 64 — 68. Galvanometers, 68 — 70. Horse-shoe temporary 
magnet, 11 — Id. Decomposition cell, voltameters, poles, 74 — 84. 
Laws of voltaic decomposition, 85, 86. Table of chemical equiva- 
lents, SI. Fluidity necessary to decomposition, 88. Conduction of 
fluids associated with decomposition, 88—90. Intensity necessary for 
decompositions, 91. Electrolysis; electro-chemical decomposition, 
92—98. Darnell's theory, 99. State of the fluid during decomposi- 
tion, 100. Effects of heat upon fluids, 101. Curious induction, 102. 
Auhtor's theory of voltaic electricity, 103. 

(59.) After describing th* various forms of the galvanic 
battery, we are led to consider the effects which they pro- 
duce ; for these are called the galvanic effects, and the theo- 
retical principle which causes them is termed galvanism. 

The sign of a battery in action, is the change going on in 
each cell of the battery itself. In Daniell's battery it is 
evinced by a deposit of copper on the negative metal ; in 
Grove's battery, by the evolution of nitrous fumes ; and in 
mine, by an evolution of hydrogen. These several actions 
mark exactly the quantity of current passing ; but in the two 
former batteries no accurate measure can be readily made, 
although in the latter the hydrogen may be collected in one 
of the cells by means of a glass jar, and the quantity thus 
exactly ascertained. 

In my battery, as the hydrogen passes off from the silver 
it causes various sounds. When the current is feeble, it makes 



Harris's galvanometer. 35 

a gentle singing sound • when more electricity passes, it 
hisses ; but when it is giving off its gas at the utmost power, it 
roars, the liquid bubbling and boiling from the astonishing 
quantity of gas evolved. Formerly, when I resided in the 
Bank, I had a long room, and, when trying the experiments 
necessary for my former editions, there were frequently not 
less than fifty or sixty batteries at work. From habit and 
custom the sound which ought to be elicited was so familiar, 
that in the middle of the night I could enter that apartment 
in the dark, and detect any battery which was following 
its own course instead of complying with mine. 

(60.) The next phenomenon which a battery displays is 
the power of heating conducting substances according to the 
amount of current which is actually passing, and the resist- 
ance which they afford to its passage ; and by this the most 
infusible metals, as platinum, palladium, gold, copper, iron, 
and steel, may be instantaneously melted. The size of the 
wires melted will depend upon the quantity of electricity 
developed, while the length will depend upon the intensity 
of the current. Mr. Snow Harris has ingeniously taken 
| advantage of this property to make an instrument for 
measuring the voltaic current. It consists of fine wire 
passed through a delicate air thermometer, and the expansion 
of air shows the degree to which the wire is heated. This 
instrument is a valueless test, unless both thick and thin 
wires be used in two experiments, for otherwise but one 
property of the battery is estimated. 

Conducting liquids may be heated in a similar manner. 
This fact may be seen in a great varity of ways ; dilute 
sulphuric acid may be made to boil in a syphon connecting 
two vessels in which the poles of an extensive series of 
batteries are placed. Another mode of showing the same 
fact is to take a piece of string and moisten it with acid, 
and connect the extremities with the poles of a series of 
galvanic batteries, when it will begin to smoke and become 



36 SPARK. 

charred from the heat produced. The same fact may be 
shown by drawing a fine tube to a capillary point, which is 
to be filled with dilute acid, and placed in a glass of the 
same fluid. An electrode of an intense galvanic battery is 
then to be placed in each vessel, when bubbles, probably of 
steam, will be found at the capillary opening, causing a 
series of little reports, which may be heard distinctly at a dis- 
tance of seventy or eighty feet. 

(61.) The next property which a battery displays, is its 
power of igniting metallic or charcoal points, when joined 
to the two ends of the battery, and held so that they barely 
touch ; a light is then exhibited equal in brilliancy to that 
of a little sun. This has been called the spark, and much 
controversy has taken place among the learned as to the 
distance at which the spark will pass. Some have asserted 
that it will pass through some distance ; Jacobi, however, 
considered the distance to be extremely small ; but Mr. 
Gassiot fitted up 100 series of Professor Daniell's largest 
batteries, but with them by the most delicate micrometer he 
could not discover that the spark would pass at any appre- 
ciable distance ; on the contrary, this large battery w r ould 
remain quite inert if the poles were separated by the dis- 
tance of the thinnest film of paper. In a late number of the 
Philosophical Magazine, Mr. Crosse has revived the inquiry 
by stating that by a very extensive series of water batteries 
in his own possession he has succeeded in obtaining the spark 
at a short distance. He proposes to enlarge his battery to 
100 cells, in order fully to determine this point. Since 
that period the experiment has been tried with 100 cells of 
Grove's battery, belonging to Mr. Gassiot ; but the spark 
was only found to pass through the smallest interval, and a 
most brilliant arc of flame was obtained after the poles were 
connected and then withdrawn. 

The spark seems principally to depend upon a combustion 
of fine particles of metal, and, when charcoal or hard gas 



PHYSIOLOGICAL EFFECTS. 37 

• coke is used, upon little points of it flying from one pole to 

e another, so that one pole wastes away, and the other in- 

; creases, till the flame becomes quite encased in a mass of 

' carbonaceous matter. This has always been an obstacle to 

the adaptation of this brilliant arc of flame to practical 

purposes. The phenomenon of the spark requires a series 

for its production. Of late years exhibitions of the electric 

light have been publicly made at Trafalgar Square, and it 

; has even been introduced to give increased effect during 

the performance of ballets at the Opera House. It is, 

! however, too costly for general purposes, although where 

1 expense is no object it might be employed. This arc of 

flame is singularly repelled or attracted by a magnet held 

c in its vicinity. 

(62.) The next property evinced by the galvanic battery 
i is its power of charging a Ley den jar ; but this is a property 
of little importance, and requires an extensive series of bat- 
teries to be used to effect this object. 

(63.) Depending upon the same causes as the last is the 
shock, which is a convulsive twitching in the muscles from 
i the intensity of the battery. This singular effect requires 
generally a series. It is felt only when contact is either 
made or broken ; but if a cut exists in the finger, a small 
series will illustrate this property. 

When we desire to exhibit the effect of the shock upon a 
dead animal, a pin ought to be run through the skin at the 
head, and another at its hind leg ; every time the poles of a 
battery are connected or disconnected with these, strong 
convulsions will take place. If the upper lip be touched 
with a piece of zinc, and the under part of the tongue with 
a piece of platinum, or vice versa, a flash of light will be 
perceived when they are connected, whether the eyelids be 
open or closed. All these phenomena are termed the physio - 
; logical effects, and I have amply considered their importance 
in my " Elements of Electro-Biology." 



38 MAGNETISM. 

(64.) A galvanic battery has the power of producing cer- 
tain effects which are called magnetic effects, and the sup- 
posed principle of magnetism. To describe the term mag- 
netism would be impossible, like galvanism, or electricity, 
because we are only cognizant of it by its properties. There 
are but two metals capable of being magnetic, and these are 
nickel and iron. The identity of magnetism and electricity 
has, like all other branches of philosophy, received many 
important additions from the indefatigable Faraday ; but, 
although magnetism is fraught with interest, it will be 
foreign to the purpose of this work to enter farther into its 
important details than to illustrate the effects of galvanism. 

(65.) The voltaic current, passing at right angles to a 
piece of iron, from which it is separated by any non-con- 
ducting substance, induces in it the properties which are 
termed magnetic ; for, if another piece of iron be now held 
to it, it will be attracted. The more frequently the same 
current passes round the iron, the greater will be the power ; 
and for this purpose it is usual to twist wire covered either 
with silk or cotton round the iron, in order that the same 
current may pass at right angles a great number of times. 
When the current ceases, from the connection with the 
battery being broken, a difference according to the nature 
of the iron is observed ; for, if it be the pure malleable soft 
iron, all magnetism immediately ceases ; hence iron so 
situated is termed a temporary magnet : but if hard steel 
is used for the experiment, the magnetism indeed is not so 
powerful, but it continues for a very long period ; hence in 
this state it is called a permanent magnet. 

(66.) A permanent magnet, if suspended in such a way 
that it can vibrate, has one of its poles turned to the north 
pole of the earth, the other to the south pole ; but, if a 
galvanic current be passed round this permanent magnet in 
the direction of its axis, the magnet will be instantly 
deflected at right angles from the current, and upon this 



MAGNETIC GALVANOMETERS. 39 

principle an instrument has been constructed called the 
galvanometer. 

(07.) The direction in which the needle is deflected is 
best remembered by a little device which Professor Daniell 
described in his lectures ; for by supposing that we ourselves 
are the conducting wires, and the electric current passes 
from our head to our heels while we are looking at the 
magnet, the north pole will be turned to our right hand. 
This ingenious device is applicable to every position, pro- 
vided we are either above or underneath the plane of the 
needle. 

(68.) Galvanometers are differently constructed, according 
to the delicacy of the experiments for which they are re- 
quired. In general it is sufficient to use a needle centred 
as if it w r ere to be j^ # 6. 

used for a mariner's 
compass, and a long 
covered wire is to 
be passed alternately 
over and under it in 
the direction of the long axis. The two ends of the wire may 
be connected to mercury cups (p, n), to afford a ready 
means to unite them with the poles of the battery (Jig. 6), 

(69.) A much more delicate form of galvanometer is con- 
structed by using two needles, so suspended "that the north 
pole of one is over the south pole of the other. 

The polarities are thus neutralised, and no longer under 
the influence of the earth's magnetism. In this state they 
are called astatic, and are generally suspended by the finest 
fibre of silk, so that the slightest voltaic current will act upon 
them. 

It is advisable to allow one needle to have a slight prepon- 
derance, in order that the long vibration may not be trouble- 
some. An instrument like this is only necessary for the 
most minute experiments. 




40 MAGNETISM A TEST OF THE QUANTITY OF ELECTRICITY. 

(70.) Another form is termed the torsion galvanometer, 
because a resistance is afforded by the twisting of an elastic 
substance. By this we are enabled to appreciate differences 
in slight currents. 

(71.) However useful the instrument may be for all small 
currents, large quantities of electricity are seldom measured 
by magnetic effects ; but I believe that the right use of the 
magnet is a very important addition to our instruments for 
measuring galvanic currents. To estimate the quantity of 
electricity in any voltaic current, a piece of soft iron is to be 
bent in the form of a horseshoe, and a good sized covered 
copper wire is to be wound round it, the two ends being left 
free for connection with the battery. A piece of soft iron 
with a hook attached to it is to be used for the keeper, 
and the weight which this sustains indicates the amount of 
electricity. 

This instrument is only valuable for comparative experi- 
ments, as different results will always be obtained by different 
magnets, because the quality of iron is found materially to 
influence the results ; but if the same magnet be used, and 
the w T ire of sufficient dimensions and of moderate length, 
there will be scarcely any appreciable resistance offered to 
the current ; and the relative quantity of electricity evolved, 
independently of its intensity, can be accurately ascertained. 

(72.) Temporary magnets are too frequently made with 
very thin covered wire, and even great lengths employed. 
Now, in this case, the amount of magnetism induced by any 
current ceases to be an exact measure of the quantity of elec- 
tricity passing, because intensity is required to overcome the 
resistance afforded to the passage of the current from the 
wires ; and it is from this cause that electro-magnetic engines, 
possessing, as they do, several magnets, and very often thin 
wires, require several cells before the current freely passes. 

(73.) To give a comparative estimate of the value of this 
test of the quantity of electricity evolved, and of that There- 






DECOMPOSITION APPARATUS. 41 

by the power is estimated by decomposition, perhaps is pre- 
mature, till the latter mode is fully entered into ; but as the 
magnet requires but little intensity, or affords but little re- 
sistance to the passage of the galvanic fluid, and that entirely 
depending upon the size of the wires, it is apparent that one 
cell of each combination, or form of battery, w T ill suffice for 
the experiment : if, however, the decomposition of water be 
taken as the test, a sufficient number of cells must be em- 
ployed to overcome the resistance ; and thus, if many 
combinations are made the subject of experiment, it will be 
attended with great inconvenience. 

(74.) If the various effects which have been already de- 
scribed are fraught with interest and mysterious obscurity, 
how much more is the property, which the battery possesses, 
of decomposing various substances, and of overcoming the 
most powerful affinities by which bodies are united ! To 
this part of the subject we are again indebted to the labours 
of which the Eoyal Institution has been the principal seat, 
and Sir Humphry Davy and Faraday the authors, though 
Daniell and many others have been by no means behindhand 
in the field of inquiry. 

(75.) The decomposing cell is to be reckoned as one of 
the cells of the battery, with variation in the metals and 
solution for the purposes of experiment. Formerly the size 
of the plates of this cell was reckoned but of little importance, 
mere wires were employed ; but now the plates are made 
much larger. This fact has been particularly insisted upon 
by Mr. Grove, and certainly it is a circumstance to be fully 
attended to. Throughout this work abundant instances 
occur of the importance of the size of the plates, poles, or 
electrodes in the decomposition trough, for there is not a 
single electro-metallurgical operation which may not be 
materially influenced by either varying the size of both poles, 
or by diminishing or reversing their relative surface. In 
some cases, indeed, where there is such a powerful resistance 

4 



42 VOLTAMETERS. 

afforded by the evolution of the oxygen at the positive pole, 
this effect is not manifest ; but even in that case, if it be re- 
duced to a fine wire, I have seen a battery, capable of evolving 
30 cubic inches of gas in five minutes, not able to evolve 
from the diminished surface scarcely one cubic inch in the 
same period. When a metal is used capable of combining 
with the oxygen, as silver or copper, then the size of the 
poles makes important alterations, even if large plates are 
employed. We shall hereafter see, that in the reduction of 
every metal these properties must not only be remembered, 
but acted upon, if we wish to perform our operations with 
success. 

(76.) There are many forms of the decomposition cell which 
are useful, according to the purpose for which it is wanted. 
The simplest is the V-shaped tube, Fig. 1. 

which is nothing but a glass tube ^ 
bent in the shape of the letter from 
which it derives its name. A little 
strip of platinum is to be placed in 
either part with the fluid, and these 
are to be connected, one with the negative, the other with 
the opposite pole of the battery. 

(77.) The next form was devised by Professor Faraday, 
and is adapted to measure the quantity of gas given off when 
water is decomposed. To this he gave the name of volta- 
meter, as indicating the amount of electricity passing. Of 
this form there are many varieties, differing as a small or 
large quantity of gas is required to be measured. In the 
former case, two pieces of platinum are fixed about a quarter 
of an inch apart, arid a tube, graduated to cubic inches, is 
supported over these poles so that the gas may be collected. 
Sometimes two tubes are employed, one over each pole, the 
object of which is to collect separately whatever may be 
evolved. In other cases, where large quantities have to be 
estimated, a bent tube passes from the top of the apparatus 




VOLTAMETERS. 



43 



to a graduated jar placed in a pneumatic trough. Where 
great accuracy is required in the measure of the gas or gases 
Fig. 8. 




Fig. 9. 




evolved, they must be corrected hygrometrically, thermome- 
trically, and barometrically ; but this nicety would only be 
required for most delicate experiments. This instrument is 
made more complicated when the operator is desirous of 
investigating the changes which take place in the solution ; 
for then porous tubes of earthenware, bladder, &c. are used 



Fig. 10. 



to separate the poles, and to pre- 
vent the solution on one side passing 
freely to the other. Substances re- 
quiring heat to bring them into a 
state fit for decomposition are gene- 
rally placed in a tube containing two 
fine platinum wires, which serve as 
poles when connected to the battery. 

A very useful form of decomposition apparatus is a vessel 
with a diaphragm {fig. 10.) or a glass tumbler {fig. 11.) (t) 
cut in half, and the edges ground smooth : between these 







44 ELECTRODES, ANODE, CATHODE, ETC. 




any diaphragm (d) can be placed, as the two halves are 
kept firmly together and water-tight, by Fig. 11. 

a brass band surrounding them (b). 

(78.) Having described the usual ap- 
paratus to effect decomposition, we have 
seen that in every case they have in 
common two pieces of metal, separated 
from each other, but capable of being 
connected to either extremity of the 
battery. These pieces of metal have the mysterious and in- 
comprehensible names of poles ; one of which may be con- 
sidered as holding the place of the negative metal, and is 
called the electro-negative pole ; and the other, the electro- 
positive pole. 

(79.) However, Dr. Faraday, disapproving of the name of 
poles, has called the electro-negative the cathode ; and Pro- 
fesser Daniell, disapproving of both, has called it the platin- 
ode. These three terms, the electro-negative, cathode, and 
platinode are synonymous, and are given to that pole which 
would have been the metal unacted upon, had it been in an 
ordinary cell of the battery. The opposite pole holds the 
same place in the decomposition cell as zinc in the ordinary 
battery, and technically has the name of the electro-positive, 
anode, zincode, or oxode of the battery. 

Dr. Faraday has described the poles as the passages or 
doors by which the electricity enters into, or passes out of, the 
solution suffering decomposition. On this account he has given 
the term of electrodes. Good conductors are the best adapted 
for poles, and for this reason metals are generally employed ; 
but poles of water, and even of air, have served this office. 

(80.) The metal employed for Faraday's voltameters should 
undergo no change either from the solution in which it is 
placed, or from the elements which may be evolved at its 
surface ; and in this respect platinum answers above every 
other substance, for almost all other metals are liable to be 
oxidized, or even dissolved. 



DECOMPOSITION CELL. 45 

(81.) The greatest confusion has arisen by not considering 
the decomposition cell as one of the cells of the battery, but 
referring the effects to the plate of the battery to which the 
pole is connected. The reason of this is obvious ; for, when 
the terminal plates of a battery are connected with a wire, 
the circuit is completed, and the platinum of the battery is 
the platinode, electro-negative, cathode, or hydrogode of the 
battery. When the circuit is completed by a liquid to be 
decomposed, the effect is no longer to be attributed to the 
terminal plates of the battery, but to the plates in the de- 
composition cell with which they alternate ; so that, as the 
free zinc of the battery is connected with the platinum of 
the decomposition cell, the name must not be given from the 
zinc of the battery, but from the platinum of the decompo- 
sition cell ; and, therefore, it is the platinode of the battery. 
The converse of this applies to the extreme platinum of the 
battery ; for, as the platinum in the decomposition cell with 
which it is connected holds the place of the zinc in the other 
cells, the platinum being substituted for zinc, to cause the 
evolution of the oxygen and to prevent its combination, the 
name must be given to the platinum in the decomposition cell, 
which is there holding the place of the zinc, and not to the 
terminal plate of the battery ; it therefore is the zincode, 
electro-positive, anode, or oxode of the battery. Some have 
given a different explanation of this alteration of the poles, 
when the circuit is completed by a solution to be decomposed, 
instead of metallic wires ; they suppose that the two terminal 
.plates in a compound battery hold no farther place than 
that of carrying the current ; but this will not bear the test 
of inquiry. 

(82.) We have now seen that the decomposition cell, or 
decomposing apparatus, is nothing but one of the cells of the 
battery varied for the purpose of experiment ; it necessarily 
follows the law, that in every cell there is a similar amount 
of chemical action. The measure of electricity by the chemical 



46 VALUE OF THE VOLTAMETER. 

action may be made in any other cell in a great variety of 
other ways, such as by ascertaining the amount of the reduc- 
tion of any metal at the negative pole, or the solution of a 
metal at the positive pole ; for, wherever it is made, it will 
indicate exactly the action taking place. To Faraday these 
important facts are due, which, perhaps, have given us a 
greater insight into the properties of the galvanic fluid than 
any other series of inquiries. 

(83.) Of the value of the decomposition apparatus, or 
voltameter, it is necessary particularly to take notice. As 
far as the amount of chemical action actually passing is con- 
cerned, the voltameter is a most valuable test, being in all 
ordinary circumstances infallible. But if we are desirous of 
comparing the amount of electricity capable of being gene- 
rated by combinations of different metals, or the effects 
which are produced by differences of arrangement, or the 
resistance which various substances offer to the passage of 
the current, then it must be recollected that, if two pla- 
tinum poles are employed, a strong resistance is offered to 
the passage of the current by the positive platinum pole, 
which would materially interfere with the accuracy of th 
result, unless that be overcome. In fact, the voltameter is 
an accurate test of that electricity which actually passes 
in a galvanic circuit, but it does not at all indicate what 
might pass. A want of application of these facts has led 
many distinguished scientific chemists into singular blunders, 
and many circumstances have not been appreciated which 
would otherwise have been noticed. 

(84.) A far better voltameter can be constructed by using 
one of the cells of the platinised silver battery, and collecting 
the gas evolved from the negative plate. This apparatus 
would offer but little resistance to the passage of the elec- 
tricity, and would thus give more accurate results ; but it 
has the disadvantage of itself generating electricity, thereby 
increasing the power. Practically, it is exceedingly difficult 



VALUE OF THE VOLTAMETER. 



47 



Fig. 12. 



to compare exactly the power of any two batteries or combi- 
nations ; for there are such a number of resistances in the 
galvanic circuit, and these vary with every battery, that it 
becomes quite a complicated mathematical problem to analyse 
the precise relative power of galvanic batteries. My battery 
voltameter is constructed in the following way : — a bell glass 
is procured with a bent glass tube ground into the upper 
part to allow the gas to pass off to the pneumatic trough to 

be collected (a). In the bell- 
glass a piece of platinised silver 
is placed, which is connected by 
means of a piece of silver wire 
running through the glass to a 
binding screw outside the glass. 
The whole of the apparatus is 
plunged into another glass filled 
with dilute sulphuric acid, at the 
bottom of which is mercury and 
pieces of waste zinc; a silver 
wire connects this to another 
binding screw, to finish the con- 
nection, when the apparatus is 
ready for use. This instrument 
is extremely valuable when we desire to measure the 
work done with a single battery, for it makes not only a 
voltameter, but the battery itself. When we are compelled 
to make an experiment with extreme accuracy, we might 
vary the apparatus a little, so that the hydrogen arising 
from any trifling action on the zinc may not be collected 
along with that obtained from the voltaic decomposition. 
The zinc in that case should be placed exterior to the inner 
vessel. 

(85.) When we state that the action in each cell is alike, 
it is not meant that the same weight of metal or salt would 
be decomposed in each cell, but that one equivalent of some 







48 CHEMICAL EQUIVALENTS. 



substance is decomposed in each cell : thus for one grain of 
hydrogen liberated in one cell, 86 grains of chlorine would 
be liberated in a second, 96 grains of platinum in a third, 
and 200 of gold in a fourth, because these are the chemical 
equivalents, or combining numbers, of each of these separate 
substances. 

(86.) The very term chemical equivalent seems to mark 
that it relates to something not very intelligible, and unfor- 
tunately that is found to be too correct, for this doctrine is 
found by all beginners to be exceedingly difficult. How- 
ever, by granting one supposition, the whole mystery is 
cleared up ; for let us fancy that every elementary body is 
capable of being divided into ultimate atoms, and that the 
atoms of these are of different sizes and different weights, 
it will then be apparent that, if we group these atoms 
together to form any compound, we shall require different 
weights. Thus, if we combine gold with hydrogen, 200 
grains of the first would only take one grain of the last, and 
yet there would be but one atom of each; or if one grain of 
hydrogen is liberated in the battery, 200 grains of gold 
would be deposited in the decomposition cell. 

(87.) The following is a table of the equivalents of many 
of the substances which we shall have to speak of in this 
work ; for our present purpose we may consider them as the 
weight of the primitive atoms. Thus, if we are able to 
ascertain the weight of zinc dissolved, of hydrogen evolved, 
or of the metal reduced, we shall be enabled to ascertain 
either of the other cases, or how much, either in weight or 
bulk, of any other substance would have been under the 
same circumstances thrown down : — 



Equivalent, by weight. 




Equivalent, by weight. 




Hydrogen - 


1 


Potassium 


40 


Oxygen 


8 


Sulphur - 


16 


Chlorine 


36 


Zinc 


32 



CHEMICAL Oil VOLTAIC EQUIVALENTS. 



49 



Equivalent, by weight, 
Lead - 


104 


Tin -;*-.■-.■:- 


58 


Iron - - - 


28 


Copper 
Gold- 


32 
200 


Platinum - 


96 


Palladium - 


54 


Silver - 


110 


Nickel 


28 


Chloride platinum 


132 



Equivalent, by weight. 

Chloride gold - - 308 

Sulphate copper - - 125 
Nitrate copper, anhydrous 94 

Sulphate zinc ? - 143 

Sulphate iron - - 139 

Nitrate silver - - 170 

Sulphuric acid - - 40 

Nitric acid 54 

Muriatic acid - - 37 

Ammonia - - - 17 



As 100 cubic inches of hydrogen weigh 2 grains and 1-1 0th, 
it follows that, for every 47 cubic inches of gas evolved 
from my battery, 32 grains of copper, 96 of platinum, and 
200 of gold, would be reduced ; and the equivalent of e very- 
other substance would show in grains the quantity thrown 
down. I shall frequently use the term " an equivalent of 
galvanic power," by which is meant that amount of power 
which is necessary to cause the evolution of one grain of 
hydrogen, 200 of gold, &e. ; therefore, whenever I use that 
expression, the grain will be taken as the standard, and it 
will be assumed that 47 cubic inches of hydrogen are 
evolved from my battery. 

(88.) Next to the form of apparatus for decomposition, a 
description of the laws by which they are influenced follows 
as a natural sequence, and these have been fully investigated 
by the labours of Dr. Faraday. All bodies must be in a 
peculiar state to suffer decomposition, for no solids can be 
thus acted upon. When fused by heat, however, they very 
readily give up these elements ; as, for example, chloride of 
silver, which is decomposed by a single cell of zinc and pla- 
tinum, excited by dilute sulphuric acid, though no voltaic 
power will separate them in the solid form. 

There are apparent exceptions to this law, as the decom 

4* 



50 FLUIDITY ESSENTIAL FOR DECOMPOSITION. 

position of sulphate of lime and baryta with the addition of 
water ; yet the first of these is undoubtedly moderately 
soluble. The same may perhaps even be said of the latter, 
though probably a little dissolves which is decomposed, and 
thus the fluid not being saturated dissolves more, and this is 
repeated till the whole is dissolved. 

(89.) No fluid will be decomposed unless it be a con- 
ductor : thus pure water, which is a very bad conductor, 
does not yield up its elements ; whilst if acids or alkalies be 
added to it, then it becomes a very excellent conductor, and 
is easily decomposed. Water may also be made a good 
conductor by the neutral salts. 

As a general rule, fluids will not conduct an electric cur- 
rent without suffering decomposition ; and for this cause, as 
soon as water is made a good conductor, it is decomposed, 
and the water does not conduct more electricity than is to be 
accounted for by the decomposition. 

(90.) Some fluids, however, of good conducting power, may 
have a current of less intensity than that which is required 
for the decomposition passed through them ; therefore these 
two laws, both developed by Faraday, are not exactly the 
converse of each other. Examples of the exception to the 
second are to be found in chloride of lead or fused nitre, 
which conduct feeble currents without decomposition. 

(91.) A certain intensity is necessary to effect all decom- 
positions, and this differs with different substances, according 
to the resistance they offer to the passage of the galvanic 
fluid ; thus, a solution of iodide of potassium, or fused chlo- 
ride of silver, yields to a single battery, whilst dilute sul- 
phuric acid and other substances require more intensity to 
effect the same object. 

The following, upon the authority of Faraday, is a short 
list of substances in the order in which they most readily 
give up their elements : — 



ELECTROLYSIS. 51 

Iodide of potassium, solution. 

Chloride of silver, fused. 

Proto-chloride of tin, do. 

Chloride of lead, do. 

Iodide of lead, do. 

Muriatic acid, 

Water, acidulated with sulphuric acid. 

(92.) Some bodies suffer decomposition directly, as the 
consequence of the voltaic force passing ; as water, which 
gives up its elements,. hydrogen and oxygen, solely from the 
electric currents. To this Dr. Faraday has given the term 
electrolysis, because the elements appear to be rent from 
their combination directly by the voltaic force, in contra- 
distinction to another important property, which will 
be hereafter mentioned. The elements which are decomposed 
he has called ions ; they are not both evolved at one pole, 
but one at the electro positive, anode, zincode, or exode, 
while the other is given off at the electro-negative, cathode, 
platinode, or hydrogode of the battery. Those which pass 
to the first pole are called anions ; those to the second, 
cathions. 

(93.) The poles, or electrodes, have no attraction for ele- 
mentary bodies as long as they are in a simple state, for 
bodies must be in combination to be affected by the voltaic 
current. Upon this account, a simple solution of chlorine, 
bromine, &c, does not give up these substances to either 
electrode. 

(94.) Those bodies capable of suffering decomposition 
must contain one equivalent of each element, that is, they 
must be composed of one of the hypothetical atoms, which 
have been previously mentioned (87) ; and to this general 
law but a single exception can be found in the periodide of 
mercury, which however is so unstable a compound, that the 
slightest exposure to light will cause its decomposition, 



52 ANIONS, CATHIONS, ETC. 

which alone would be calculated to throw doubt on the va- 
lidity of the experiment. 

Sulphuric acid and phosphoric acids are not themselves 
electrolytes, that is, they do not directly yield their elements 
to the force of the battery, because they consist of one 
equivalent of phosphorus or sulphur to three of oxygen. 

(95.) It is not necessary that a substance should be directly 
composed of elements to enable it to pass to the electrodes or 
poles ; or, in other words, bodies composed of compound sub- 
stances are ions, as well as those composed of simple sub- 
stances : thus, sulphuric acid, phosphoric acid, arsenic acid, 
and other acids are ions to the electro-positive pole, or 
anode ; while protoxides generally, ammonia, potassa, and 
many other substances, are supposed to be ions to the oppo- 
site pole. The following is a list of simple and compound 
ions given by Dr. Faraday : 

Anions : 



Oxygen, 


Fluorine, 


Selenium, 


Chlorine, 


Cyanogen, 


Sulphocyanogen, 


Iodine, 


Sulphur, 


Acids. 


Bromine, 







Cathions : 
Hydrogen, Alkalies, 

All the metals, Vegeto alkalies, as 

Metallic oxides, morphia, &c. 

The earths, 

(96.) The same substance, under different circumstances, 
will be evolved at different electrodes ; as at one time it may 
take the part of a base, at another it will perform the func- 
tion of an acid. A familiar example of this is afforded in the 
oxide of copper ; for when combined with sulphuric, nitric, 



ELECTRO-CHEMICAL ACTION. 53 

muriatic, or any other acid, it is evolved at the negative pole, 
or cathode; whilst, when in combination with ammonia, it 
has been supposed to act the part of an acid, and is evolved 
at the anode or positive pole. 

(97.) The opinions of philosophers upon the cause of 
metals being reduced when solutions of their salts are sub- 
jected to the voltaic circuit, from the period when electricity 
first lent its mighty aid to chemists, are various. Some have 
supposed that hydrogen evolved by the decomposition of 
water reduces the metals, others that the poles directly attract 
the metals to their surfaces, and lately a paper has been 
printed in the Transactions of the Royal Society, whereby a 
new constitution of the salts is inferred ; the acid and oxygen 
being supposed by electrolysis to pass in one direction, the 
metal in the other. The first opinion was put forward by 
Hisinger and Berzelius, and may be found in the Annates de 
Ckimie, vol. li. p. 174. " II resulte de tous ces faits, que 
Ton a une idee fausse de la reduction operee par l'electricite, 
puis qu'on l'attribue au degagement de l'hydrogene, comment 
expliqueroit-on la reduction du fer et du zinc, qui ont la 
propriete de decomposer l'eau sans electricite." 

A similar opinion has been advocated by Faraday in the 
Philosophical Transactions, and he applied a new name to 
this kind of action, giving it the term electro-chemical action. 
The second hypothesis was promulgated by Sir Humphrey 
Davy, who states, u that hydrogen, the alkaline substances, 
the metals, and certain metallic oxides are attracted by 
negatively electrified metallic surfaces, and repelled by posi- 
tively electrified metallic surfaces ; and contrariwise, that 
oxygen and acid substances are attracted by positively electri- 
fied metallic surfaces, and these attractive and repulsive 
forces are sufficiently energetic to destroy or suspend the 
usual operations of chemical affinity."* 

* Phil. Trans. 1807. 









k 



54 ELECTRO- CHEMICAL DECOMPOSITION. 

If we then find a body at the pole of the battery, it 
is by no means certain that it has passed by direct decom- 
position of the voltaic current ; because, if the compound of 
which it formed a part, was dissolved in water, the elements 
of the latter being set free, often act in an important way to 
form new combinations, which result from the secondary 
effects ; thus an aqueous solution of a metallic salt, for in- 
stance copper, being subjected to a voltaic current, has hy- 
drogen presented at the cathode, and oxygen at the anode. 
But at the same time this change is taking place, oxide of 
copper is passing to the cathode, and sulphuric acid to the 
anode. The hydrogen seizes upon the oxygen of the oxide 
of copper, and forms water, whilst the metallic copper is 
thrown down on the electrode or pole, not by direct voltaic 
action, but as a secondary effect, attributable to the hydrogen. 
Sometimes the elements will combine with the poles or elec- 
trodes, forming new combinations ; thus, if the poles be easily 
oxy dated, the oxygen will form an oxyde, and, in the same 
way, if any other substance be presented to the gases for 
which they have strong affinity, a similar combination will 
take place. Hence this class of effects, which are far more 
numerous than electrolytical effects, are called secondary, or 
electro-chemical decompositions. Sometimes these secondary 
results are most complicated, and perhaps none more so than 
the extraordinary one which I have described to take place 
with the oxygen, on the common yellow ferrocyanate of 
potash ; as this, by combining with a portion of the potassium 
of the ferrocyanate, gives rise to a totally new definite salt,* 
whilst the potash so formed is carried away from the sphere 
of action. 

(98.) The secondary effects of oxygen and hydrogen have 
been proved by numerous well-devised experiments, but still 
no positive demonstration was obtained, that the hydrogen 

• Philosophical Magazine for September, 1840. 



daniell's theory. 55 

evolved from the decomposition of water, would reduce the 
metals without the voltaic current. However, whilst expe- 
rimenting on the non-metallic elementary bodies, the porous 
cokes and charcoal were observed to retain a portion of gas, 
after they had formed either the negative or positive pole 
of the battery.* When those which had been made the 
negative pole were afterwards plunged into a solution of 
sulphate of copper, they became immediately coated with 
the metal, adding positive confirmation to inductive reason- 
ing. Coke charged with hydrogen retains this curious 
property for many days.f This very interesting experiment 
has been followed by Mr. Grove by the construction of his 
gas battery. 

(99.) Professor Daniell, in a paper read before the Eoyal 
Society last spring, has given an entirely new view, as to the 
mode in which the metallic salts are sometimes decomposed. 
The Professor found if a solution of a metallic salt was placed 
in a vessel, over which a piece of membrane was tied, and 
that inserted into another containing a solution of caustic 
potash or soda, so that the membrane formed a sort of dia- 
phragm between the two solutions, and then if the poles 
of a compound galvanic battery were placed into the two 
solutions, the positive into the metallic solution and the 
negative into the alkaline solution, that the metal of the 
first solution was deposited on the bladder. This is an expe- 
riment easy to repeat with several solutions, especially silver, 
mercury, and copper, though with gold and platinum the 
same result does not appear to take place. If acids or neu- 
tral salts be employed, instead of the alkaline solutions, I 
have never seen metal deposited on the bladder. When the 
alkaline solutions are used and the metal is precipitated, gas 
is always evolved from the membrane. In these cases a 
question might be raised whether the membrane between the 

* Philosophical Magazine for May, 1840. 

•)• Philosophical Magazine for December, 1840. 






56 ELECTRO-CHEMICAL DECOMPOSITION. 

two solutions might not become polar similar, to interposed 
wires. Professor Daniell supposes that in this experiment 
the acid and oxygen pass one way, and the metal the other. 
From these considerations he has given a new view of the 
composition of the salts ; thus, sulphate of copper, instead of 
consisting of sulphuric acid + oxide of copper, is supposed to 
be constituted of (sulphuric acid + oxygen) copper. The 
first two elements, as they are considered to be in combina- 
tion, are called oxysulphion, and the salt oxysulphion of 
copper. In the same way, the radicle of the nitrates he called 
oxynitron — of the carbonates, oxycarbon — of the oxalates, 
oxalion — of sulphovinates, sulphovinion. 

In the same paper, another fact is detailed ; which is, the 
property the electric current possesses of decomposing two 
substances in the same solution ; thus, both a metallic salt and 
acidulated water may be decomposed at the same time, the 
current dividing itself between them. 

(100.) We have now seen that substances may be decom- 
posed in two ways, either from directly yielding their ele- 
ments to the voltaic current, when the compound consists of 
single equivalents, which is termed electrolysis, or, by a se- 
condary action which occurs oftentimes, as a result of a new 
decomposition by or combination of the elements of the first 
substance decomposed, upon a second substance within the 
sphere, which secondary action is termed by Dr. Faraday 
electro-chemical decomposition. 

The fluid between the electrodes, whilst decomposition is 
taking place, apparently undergoes no change ; that is, the 
effects of the decomposition are only manifested at the poles ; 
thus, if sulphate of copper be electrolysed, sulphuric acid 
passes one way, oxide of copper another ; yet neither acid 
nor odide can be found in any part intervening. These ex- 
periments are best conducted in a long flat vessel with two 
porous plates, which divide it into three departments, of 
which the two exterior receive the electrodes. 



CURIOUS INDUCTION. 57 

(101.) The temperature at which the solution to be de- 
composed is kept, materially interferes with its conducting 
power"; a fluid which is a good conductor at ordinary tempe- 
ratures, will scarcely admit the passage of the galvanic fluid 
at the freezing point, whilst at the boiling point a passage 
will be afforded, with the greatest readiness. It becomes, 
therefore, a very important matter to keep solutions at a 
high temperature, when we are desirous of effecting much 
decomposition in a short time, and at a slight expense. 

(102.) The galvanic fluid, when it has the choice of a 
passage through various conducting substances, prefers that 
which affords the least resistance to the exclusion of the rest ; 
thus, if a galvanic battery of large series is connected to a 
decomposition apparatus, and is capable of giving off 20 or .80 
cubic inches of gas in five minutes, yet the finest platinum 
wire, on being placed across the poles, will cause the whole 
of the power to pass by the wire during the short time 
that it remains unmelted. 

A curious property of induction is observed, under certain 
circumstances, in the voltaic circuit : thus, if a wire or a 
series of copper wires is suspended in a liquid which is 
suffering decomposition, whether that be in one of the cells 
of a battery or in the decomposition apparatus, one part of 
each wire will be seen to become positive and be dissolved, 
whilst another part w T ill be negative and reduce any metallic 
salt. This phenomenon will be seen to be taking place 
differently in each of the wires. If a platinum wire be inter- 
posed in the circuit the resistance which the evolution of 
oxygen affords is so great, that the polarity of the wire is 
only to be seen in certain cases. However, feeling assured 
that platinum could be made polar, I set to work with deter- 
mination to effect it, I tried large plates of platinum in 
sulphate of copper, between two copper electrodes, connected 
with a powerful battery, but could not succeed ; however, not 
to be beaten, I tried the experiment in a different way. A 



58 CURIOUS INDUCTION. 

piece of fine platinum wire was fixed in a small tube, one 
part remaining in the inside, the other on the outer part of 
the vessel ; a small hole was then left in the tube, of such a 
size that water could freely run out. The tube was filled 
with dilute acid, and placed in a glass full of the same liquid, 
when the pole of a series of batteries (not less than 8 cells) 
was inserted into the tube, taking care that it did not touch 
the wire fastened in the tube : the other pole of the battery 
was placed in the glass of dilute acid, when immediately gas 
was evolved from the two poles, and also from the platinum 
wire. It was then thought desirable to ascertain whether 
as much gas was evolved from the intermediate platinum 
wire, in which the gas was given off by induced electricity, 
as from the original poles. This point was determined upon 
the principles which regulate electro-metallurgical operations, 
for upon the addition of a small quantity of sulphate of 
copper to the acid, the pole connected with the zinc of the 
battery was coated with spongy copper, whilst the part of 
the intermediate platinum wire which became negative had 
the bright reguline copper reduced on its surface. The rest 
of the intermediate wire was positive, and evolved oxygen 
gas. It is a matter of great interest to ascertain whether 
non-conducting substances could be made polar in a similar 
way, but all the evidence with me has varied sometimes one 
way and sometimes another; and I am quite uncertain 
whether they may be made polar or not. Of course the 
smallest portion of any solid conducting substance, as the 
smallest atom of charcoal or plumbago, will instantly become 
polar and give off gas. This kind of induction is inter- 
esting as explaining the action which takes place on a 
binding screw or piece of copper dropped into a galvanic 
battery, or into a metallic solution, which is being decom- 
posed. 

These experiments have obtained additional importance 
from their having enabled me to determine the course of the 




THEORY OF THE VOLTAIC CURRENT. 59 

voltaic currents in the human body, which have since been 
detailed in the Elements of Electro- Biology. Upon the prin- 
ciple which may be inferred from these experiments, the 
electro-voltaic test for voltaic currents passing through fluids 
was obtained. The following apparatus well illustrates the 
principle. 

The diagram consists of two gutta percha tubes, contain- 
ing dilute sulphuric acid, 
and two series ' of plates Fig. 13. 

of zinc (z) and platinized 
silver (s). By the intro- 
duction of two copper 
wires into one of the 
tubes the presence of 
the current will be in- 
dicated by a galvanometer. 

(103.) In this place perhaps it may be advisable to give 
my own theory of the voltaic circuit. I claim for this theory 
no infallibility, and I offer it merely as an epitome of the 
results which have been obtained during the experiments 
necessary for writing this volume. I ask, however, my 
reader to adopt it whilst studying the experiments hereafter 
to be detailed ; but as soon as the theory has been used to 
help him to obtain the facts, I beg him to discard the theory 
and hold to the facts as he himself observes them, that, in 
his own mind, he may hold that theory which expresses the 
facts with which he has been made cognizant. 

In performing my electro-metallurgical experiments I 
noticed that in various mixed solutions the quantity of vol- 
taic force passing was not at all dependent on the nature of 
the negative element, but upon the ease with which the 
hydrogen was removed from it. Thus, in a solution of sul- 
phate of zinc very slightly acidulated, the hydrogen could 
not be evolved from smooth copper, but would rather reduce 



% 



60 THEORY OF GALVANISM. 



the sulphate of zinc when connected with a small battery. 
The substitution of smooth platinum in no way added to the 
power, but the employment of platinized platinum caused 
an abundant evolution of gas, even to the removal of the 
zinc already reduced on the smooth platinum. Any metal 
having but little affinity for hydrogen caused a similar re- 
sult ; thus, iron caused gas to be evolved and increased the 
force passing, when smooth platinum would not have the 
effect, and even zinc itself caused a little gas to be evolved, 
because the adhesion of the gas to it is slighter than the ad- 
hesion to smooth platinum. 

In the same way I observed that nitric acid allowed far 
more electricity to pass than sulphate of copper ; and that 
again, than dilute sulphuric acid, simply from the facility 
with which hydrogen reduces these substances being greater 
than the facility of its evolution. I moreover noticed in 
other cases that the hydrogen would rather be evolved than 
reduce a metallic salt, — as sulphate of zinc ; — and in every 
case that the facility of its removal affected the amount of 
power passing, quite independently of the nature of the ne- 
gative plate. 

Now these facts appeared to me a positive proof of there 
being no such thing as a negative plate contributing to the 
production of power, and that this latter is of no value, 
further than as a means for the removal of the second element 
of the intervening compound fluid. On the other hand, the 
multitude of experiments by Faraday all show that the che- 
mical action between one element of a compound fluid and 
some conducting body appears to be the source of the power, 
or rather that the power is always dependent on and propor- 
tionate to this chemical action. Putting these two series of 
facts together, an idea presented itself to my mind explana- 
tory of the nature of the voltaic force, for if the force from 
the experiments of Faraday is proved to depend on chemical 
action, and the negative pole from my own experiments is 



METALS REDUCE METALS OF LIKE NATURE. 61 

proved to be useless, except as affording the means for the 
removal of the second element of the compound fluid, then it 
follows as a natural consequence, that if the chemical affinity 
of any substance for one element of a compound fluid is 
greater than the resistance offered to the evolution of the 
second, force is produced. Now it immediately occurred to 
me that some metals might be made to reduce from a solu- 
tion of one of their own salts, metal of the same description, 
by placing the metal partly in a solution for one element of 
which it has great affinity, and partly in a solution of one of 
its salts. This was actually found to take place in various 
cases, by following the facts that were made out respecting 
the ease with which hydrogen reduces various salts. 

Zinc reduces zinc by taking a piece of the metal and 
doubling it, one half is then to be amalgamated and placed in 
dilute muriatic acid, and the unamalgamated into a strong 
solution of chloride of zinc, made as neutral as possible, when 
the affinity of the chlorine for the muriatic acid is sufficiently 
great to cause zinc to be reduced at the other end of the 
same piece of metal. The use of platinum, palladium, silver, 
copper, or any other metal, appears not to increase the action 
in the least, which experiment shows most powerfully the 
utter fallacy of the contact theory, or in other words that the 
voltaic force is in any degree dependent on the opposition of 
one substance to another. In this experiment, according to 
the advocates of this now untenable doctrine, the force should 
have set from the amalgamated zinc to the mercury, the two 
metals, according to these theorizers, having from simply 
looking at each other the property of evolving power, but 
we find that the chemical affinity determined the course of 
the current. 

Copper may by very simple means be made to reduce cop- 
per with truly great rapidity ; for if a test tube be half filled 
with sulphate of copper, and then muriatic acid be poured 
gently at the top, so that the two fluids do not mix to any 



* 



62 METALS REDUCE METALS OF LIKE NATURE. 

great extent, and a copper wire be then placed throughout 
the whole length of the tube, it will speedily show signs of 
action. The copper in the acid will rapidly dissolve, whilst 
copper will be as freely deposited at the lower part of the 
vessel. Now copper will undergo no action alone, either in 
muriatic acid or sulphate of copper. This experiment may 
be varied by the use of different acids or even some salts at 
the upper part of the vessel, for although muriatic acid shows 
this experiment most strongly, dilute sulphuric acid or mu- 
riate of ammonia will produce the same result. 

Silver reduces silver by placing one end of a silver wire 
in a porous tube containing nitrate of silver, the other in 
dilute sulphuric acid, though the metal placed in either sepa- 
rately is not affected. 

Lead reduces lead by immersing one end of a piece of 
lead in a solution of the tris-nitrate of lead, the other in 
dilute nitric acid. 

Tin reduces tin by placing one portion of a piece of metal 
in muriate of tin, the other in muriatic acid. 

Gold even reduces gold by immersing one end of a gold 
wire in the chloride, the other in dilute muriatic acid, the 
two solutions being separated as in all the former cases by a 
porous diaphragm. 

There is a beautiful experiment detailed by Mr. Grove 
which is analogous to those last described, though he attri- 
buted the results to a different cause. His experiment is to 
place two pieces of gold wire in muriatic or nitric acid, sepa- 
rated by a porous diaphragm, when no action will take place 
on either, but on being connected, that in muriatic acid will 
rapidly be dissolved, and the nitric acid will at the same 
time be decomposed by the hydrogen transferred to the other 
part of the wire. 

From the various experiments which I have examined, 
added to the extensive researches of Faraday on the chemical 
portion of the voltaic pile, voltaic effects may be defined to be 



DEFINITION OF GALVANISM. 63 

"certain effects produced by the chemical action of a body 
on one element of a compound, and manifested between 
this point of action and the evolution of the second 
element." Voltaic actions might in other words also be 
defined to be the peculiar actions evinced between the che- 
mical action of a body on one element of a compound, and 
the evolution of the second element, the point of abstraction 
and subseq uent combination of the first element being called 
the positive pole; the point of evolution or removal of the 
second element of the compound body, the negative pole. 
Hence it might be called circular chemical action, because 
the phenomenon always evinces itself as a circle. 

These definitions suit equally every possible case, and 
there is but one point included in those definitions which is 
uncertain, though as they now stand, whatever w r ay that 
doubtful case be taken, they equally apply. The difficulty, 
and the only one, that I know concerning the production of 
the voltaic force, is an uncertainty whether the force is pro- 
duced by the analysis of the compound body, or the synthesis 
of the newly-formed salt. This is a point concerning which, 
perhaps, we shall ever be ignorant, yet analogy would rather 
lead us to suppose that the combination rather than the 
analysis is the source of the voltaic force. These definitions 
show why we cannot obtain the force from the union of two 
elements ; indeed, we can never hope to obtain voltaic power 
directly from ordinary combustion, for though the energy of 
the combination of oxygen with carbon is immense, there is 
no second element, and therefore no intermediate point at 
which the effect can be manifested. For the same reason 
no force can be obtained from the union of liquid sulphur or 
bromine with metals. 

The intensity of voltaic power being always proportionate 
to the chemical action, and being the only source of power in 
the pile, it follows, that (i) the intensity or the power which 




64 PARTS OF THE VOLTAIC CIRCLE. 

the voltaic fluid possesses of overcoming obstacles is equal to 
(f) the affinity which regulates the chemical action. But as 
we find that this power is lessened under different circum- 
stances, I=F—0. O standing for the amount which F is 
lessened by the obstacles afforded to the chemical charge. 

Let us take at once a circle and examine its properties. 
We find that the intensity of the action (i) is equal to the 
affinity (f) of the body used to 
separate one element of the Fig. 14. 

compound fluid (in the galvanic 
battery this is produced by the 
zinc and oxygen) lessened by 
the mechanical resistances af- 
forded by the removal of the 
newly-formed compound (a), by 
the obstruction offered to the 

passage of the force by the compound solution (r), by the 
imperfection of the conducting power of the solid parts of 
the circuit (c), and lastly, by the obstacle which is afforded 
to the removal of the second element of the compound fluid 
(e) ; thus we have algebraically I=F— a+c+r+e. This 
circle is supposed to consist of but a series of single atoms of 
fluid, exposed at one time to the action of the body combining 
with one of its elements, and all the resistances are supposed 
to be constant. 

Sometimes this circle is exceedingly small, the (r) con- 
sisting of but one atom of the compound, and the (c) but of 
a single atom of the body combining with one element. This 
might be called properly an atomic circle, a good specimen of 
which has heretofore been called local action. 

We must now consider the different parts of the circle in 

detail, i^the chemical affinity of a body for one element 

of a compound is immensely strong where zinc is employed, 

t he attraction of that metal for oxygen being most power- 



FORMULA OF THE VOLTAIC FORCE. 65 

ful ; but if we substitute iron, tin, lead, copper, or gold, for 
the zinc, the attraction being feeble the value of (f) would 
be reduced in various proportions, in some cases almost to 
zero. 

(a) the removal of the newly formed compound affords but 
little resistance when the new salt is soluble in the fluid and 
a sufficiency is supplied for that purpose. In batteries 
generally the removal of sulphate of zinc affords but little 
obstacle, being quickly dissolved by water. 

(r) varies very much from the extent of the interposed 
fluid, and its conducting power being very different in each 
case. It varies much in different batteries. Sometimes r is 
a very complex quantity, as when two or more fluids are used 
between the combination of one element of a compound and 
the evolution of the second. In Daniell's battery, for instance, 
it is made up of three parts, not only the resistance offered 
by dilute sulphuric acid and solution of sulphate of copper, 
but also a resistance offered by the interposed diaphragm. 
It might be made up of a far greater number of parts, for 
different parts may be of different temperatures, which alone 
(if the temperature interferes with the conducting power) 
would cause v to be complex. 

(c) the resistance of the connecting part of the arrange- 
ment is generally in batteries very slight, because we select 
metals which conduct pretty freely ; (c) may be very complex, 
by iJeing made of a variety of conducting substances, thus, 
if the connexions are made of wires of different kinds of 
metal, a different resistance is offered by each, (c) in every 
battery, is generally made up of three parts, the conducting 
power of the positive and negative plates, and the intervening 
connecting wires. 

(e) the resistance to the removal of the second element 
is generally very great, affording a considerable obstacle in 
all cases, but the differences in this respect are very remark- 
able. Ordinarily (e) is a simple quantity, but becomes com- 

5 



PARTS OF THE VOLTAIC CIRCLE, 



plex when the hydrogen is removed in a variety of ways at 
the same moment. It becomes a curious question to ascer- 
tain whether (e) might ever be made a plus quantity. If 
the force proceeds from analysis, then the use of any body 
having great affinity for the second element might cause the 
current to be increased. If from synthesis, and this is most 
probable, if not absolutely certain, (e) can never be a plus 
quantity, but always a minus. In the removal of the second 
element by decomposition of another compound body, it is by 
no means uncommon for a voltaic circuit to be formed. In 
Grove's battery the hydrogen acts upon nitric acid, forming 
water, and setting deutoxide of nitrogen, &c, free : but in 
this case the intermediate part between the combination of 
the first element and the removal of the second is only the 
atom of hydrogen ; it therefore follows that this action must 
be regarded as nothing but a series of little local batteries, 
or atomic circles, having nothing to do with the great bat- 
tery which we make available for our purposes. 

It is absolutely essential, according to our definition of the 
voltaic force, that to be enabled to apply this principle for 
any purpose, however small a quantity of the force may be 
required, that either (c) or (r) should possess a capability of 
being so far prolonged as to enable us, with the imperfect 
powers that nature has furnished us, to handle or deal with 
these intervening portions of the circuit. 

In the principal batteries now in use, their relative powers 
and attributes may be fully understood by considering each 
of the above properties in their construction. 





F 


a 


c 


e 


r. 


Grove 


large 


small 


small 


little 


medium. 


Daniell 


large 


small 


small 


much 


most. 


Smee 


large 


small 


small 


considerable 


small. 


Smooth platinum 


large 


small 


small 


enormous 


small. 



Thus the four batteries may be considered equal in the 
properties of the f, a, c, the differences being only in (r) and 



PARTS OF THE VOLTAIC CIRCLE. 67 

(e). In Grove's the (e) is so small as not only to compensate 
a slight increase in the (r) over mine as usually constructed, 
but to give a great advantage to his form of battery. In 
Daniell's the (e) is rather smaller than in mine, but that 
in practice is more than counterbalanced by the use of the 
diaphragm. Th3 effect of these properties is that f in 
Grove's is diminished but little, f in mine more, in Daniell's 
more still ; and in the smooth platinum battery by far the 
most. Thus is explained the decomposition of dilute sul- 
phuric acid between platinum plates, by one cell of Grove's 
battery, and the same result not being obtained by the 
others. This equation is not only valuable for batteries, 
but applies to every single case where any substance acts 
upon a compound fluid in such a way as first to decompose 
it, then to combine with one of its elements, and set free in 
some way the other. Thus, if potassium be cast into dilute 
muriatic acid, (f) is immensely large, potassium having a 
violent affinity for oxygen ; (a) is exceedingly small, potash 
being readily soluble in water ; (r) is almost nothing, only 
one atom of fluid being traversed by the force ; (c) is prac- 
tically nothing from the same cause ; (e) is very small. The 
result of such a state of things necessarily causes a vast in- 
tensity of action, and an explosion is the result. 

Good specimens of contrasts in the magnitude in the several 
parts of the circuit are to be seen in the relative power of 
(f), as obtained by zinc and silver ; in the relative resistance 
of (a) in the solubility of sulphate of lead and sulphate of 
zinz ; in the resistance of (r) in the conducting power of pure 
water and muriatic acid ; in the resistance of (c) in a leaden 
wire a hundred miles long, and a short silver one ; in the 
resistance of (e) in the evolution of hydrogen fro.n smooth 
platinum, and its removal by nitric acid. 

The relative degrees of action evinced by zinc, tin, iron, 
and lead upon sulphate of copper are easily explained ; (f) 



68 CURIOUS VOLTAIC CIRCLES. 

differs from being larger, (a) in being smaller when zinc is 
employed, whilst (c) (r) (e), in each case remain nearly the 
same \ (a) indeed is so large when lead is employed as soon 
to put a stop to the action. 

How intelligible is the want of action of dilute sulphuric 
acid on amalgamated zinc, if examined by our equation for 
(e) ; the adhesion of the second element, hydrogen, being in- 
creased enormously, counterbalances (f), the affinity of zinc 
for the first element, or oxygen, and no action takes place. 
Amalgamated zinc is rapidly dissolved if placed in a solution 
of salts of copper or silver, for (e) in that case is depressed, 
the hydrogen rapidly reducing the copper. Nitric acid in the 
same way does not respect the amalgamation of the zinc, for 
(e) in that case is also diminished by the removal of hydrogen 
from the decomposition of the acid. As the adhesion of hy- 
drogen to plumbago is very great, it occurred to me that the 
simple application of black-lead to zinc would, by preventing 
the evolution of hydrogen, increase (e), and therefore stop the 
local action ; but although the experiment fully succeeded, 
the plumbago so quickly came off, that I have not at present 
made any practical application of the experiment. If the 
zinc be brightly polished, the adhesion of hydrogen is so 
great that it is protected as well as though it had been 
amalgamated. 

The above cases, with all their analogies, are not the only 
ones to which the equation applies, for it will account for the 
action of bodies on each other. 

In cases of single electric affinity, as the action of sulphuric 
acid on nitrate of barytes, a compound is decomposed, one 
element enters into another combination, the other is set free ; 
a voltaic circuit is therefore produced, the parts of which are 
thus made. 

(c) Sulphuric acid ) (f) 

^ ; \ Nitric acid (e) 



CURIOUS VOLTAIC CIRCLES. 69 

In cases of double electric affinity, as the action of sulphate 
of ammonia on nitrate of barytes, a similar circuit is formed 
thus : — 

0) 



(f) ( Sulphuric acid Ammonia ) , \ 

(a) ( Barytes Nitric acid f ^ 

(r) 

In both these cases, however, we have not the means of 
increasing the (r) and (c) to a tangible size (at least I have 
never been able to do it), and at present these actions have 
been restricted to the formation of atomic circles. 

There are some cases where we can extend the interme- 
diate parts (c) and (r), and then our definition of the voltaic 
force with the formula arising from it enables us to form most 
extraordinary voltaic circles, which indeed we never could 
have formed before, unless we happened to light upon them 
by chance : thus proto-sulphate of iron, placed on one side of 
a diaphragm, and nitrate of silver on the other, will give a 
current when connected with the platinum wire, and a beau- 
tiful deposit of silver will be reduced on the platinum wire, 
on the nitrate of silver side of the circuit. 

In the same manner circuits may be formed of proto- 
sulphate of iron and chloride of gold — of proto-nitrate of 
mercury and chloride of gold — of oxalic acid and chloride of 
gold, &c. In all of which cases the metal is freely reduced 
on that part of the platinum wire inserted in the metallic 
salt. The reason why a galvanic circuit is formed in these 
cases is sufficiently obvious ; water is the electrolyte or 
compound decomposed, proto-sulphate of iron is the substance 
combining with one element, and the metallic salt affords a 
means for the removal of the second element or hydrogen, 
and, as we have the power of extending the compound (r) 
and connecting parts (c), not only an atomic circuit, but a 
working battery may be made. At the diaphragm or the 



70 APPLICATIONS OF THE EQUATION. 

point of junction of the two liquids, indeed, an atomic or 
local battery is formed independently of the general or work- 
ing battery. The following are the parts of the circuit in 
the above cases. 

(£) 

(f) ( Proto-Sulphate of Iron Platinum Wire 
*(a) ( Oxygen Hydrogen (e)* 

(r) 

' It would be extremely interesting to find every case of 
decomposition of a compound fluid obedient to the equation, 
and, indeed, there is every appearance of that being the fact. 

To form a voltaic battery or to extend the decomposition of 
the fluid electrolyte to a tangible length, it is necessary that 
some obstruction be afforded to the evolution of the second 
element at the point where the affinity acts, and that a place 
should exist where the resistance to that evolution is lessened. 
In other words at (f), it is requisite that (e) be large, and 
by lessening (e) at one distant point we extend the line 
between (f) and (e), and thus make a voltaic battery. Upon 
attending to this law I have con- 
structed the thermo and photo-vol- Ft 9- 16 - 
taic circuits,! in which light and /^>\ o$> 
heat set in motion the voltaic force. *2\ jm 
Under different circumstances the %l Ivm 
part heated is either a negative or ^pM 
a positive pole. Under the same W 
law I found smooth zinc positive to 
rough zinc, and amalgamated zinc ^53 
to smooth zinc. 

The impossibility of giving a negative tendency to a metal 
when hydrogen is removed from its surface is also perfectly 
accounted for by our equation ; for the non-evolution of 

* (a) is the removal of the per-sulphate of iron by solution ; (e) is the 
removal of the hydrogen by the decomposition of the metallic salt, 
f See Elements of Electro-Biology. 



APPLICATIONS OF THE EQUATION. 71 

hydrogen, as has been already shown, protects the metal ; so 
when a facility is offered for its removal not only is the 
direct protection removed by diminishing the value of (e), 
and (f) the natural affinity of the metal for one element of the 
fluid, having but little resistance opposed to it, begins to act, 
and the metal is therefore dissolved. 

The superior action of a rough metal in contrast with a 
smooth one is explainable on the equation most satisfactorily, 
for in the first case the affinity (f) is opposed by the resist- 
ance to the evolution of the hydrogen (#), whilst in the latter 
case (f) is so strongly opposed by (e) that no action can take 
place. Zinc shavings, which always have one side bright and 
the other rough, show this phenomenon clearly. 

Hitherto we have considered (f, a, c, r, e) in every case to 
be constant, but in many instances they are subjected to con- 
tinual variation. I do not, indeed, happen to recollect an 
instance of (f) varying to any amount, but (a) varies fre- 
quently ; in the gradual saturation of a fluid it progressively 
increases, so much so as at last to equal (f). This accounts 
for zinc ceasing to be .dissolved on the saturation of the fluid 
by sulphate of zinc, although still intensely acid, (c) gene- 
rally remains constant, (r) is very unsteady, for as in all 
voltaic arrangements the fluid is always undergoing change, 
it is therefore sure to be altered in its conducting power. 
(e) is subject to great variations from alteration of the liquid 
and other causes. 

In every case of a single battery we have seen that the 
intensity is equal to chemical affinity, minus deductions for 
the resistances to that affinity. In a compound battery the 
expression is equally simple, for .the intensity is equal to the 
sum of the affinities, minus the sum of the deductions for 
the resistances. In a series of batteries all of the same na- 



ture, i'=f— a+c + r+eX^. Sometimes (n) is very com- 
plex. For example, if a compound battery be made up of a 



72 



APPLICATIONS OF THE EQUATION, 



Grove's, a Daniell's, and my own, the values of (i) must be 
considered separately, and their sum taken. 

Fig. 16. 




The diagram exhibits well the arrangement and properties 
of the compound battery. 

A good example of the affinity of (n) is seen in the water 
battery, where (i) is exceedingly small from the deduction 
for resistances of (a) and (r) being large, but becomes am- 
plified to such a degree by (n) as to possess prodigious force ; 
indeed as it possesses a capability of being amplified infinitely 
by an infinite series completely insulated, a battery might be 
constructed powerful enough for the force to pass from one 
electrode, placed in the Thames at London Bridge, and the 
other in some river in Australia, though the resistances of 
(r) and (c) in this case, from their extreme length, would be 
very great. In every water battery, as (a) instead of being 
constant gradually increases, the power gradually declines, 
at length to nothing, The curious and wonderfully-multi- 
plying powers of (^), whereby the intensity can be increased, 
precludes our saying that the galvanic power is unable to 
effect any particular object ; for, after all, it might turn out 
that (n) was not magnified sufficiently to attain that end. 

When we are turning our power to some application it is 
very convenient to consider the purpose for which it is applied 
as a resistance, and call the deduction necessary for it, r. 
If we have a series of them alike it would be r x n. If, 



COMPOUND VOLTAIC BATTERY. 73 

however, the series is not alike, it would be r+r'+r". 
The intensity of the current here would be also equal to 
the sum of the intensities, or the intensity of the whole 
battery i', with the obstacles inherent on its construction 
deducted, minus the sum of the deductions for the resistances. 
The r is frequently very complex, as in the reduction of 
metals in a decomposition trough, where it is made up of as 
many parts as a voltaic battery. 

Having amply discussed the power of the force to over- 
come obstacles, we are led to determine the time in which 
any given number of equivalents of voltaic power can be 
obtained. Hitherto we have considered the circuit to be 
made up of a single atom of the body combining with one 
element of the compound, and if the affinity exceeds but ever 
such a trifle the deductions for its obstacles, then in time any 
amount of work would be performed, provided the current 
remained constant. A current can easily be conceived so 
feeble as to take millions of years to reduce a pound of 
copper. If the entire circuit of single atoms be increased 
at every part, in fact if the mathematical voltaic circles be 
placed side by side till they reach the size of a tunnel, then 
(w), the amount of work performed in a given time, would 
be equal to the intensity of the battery, minus the deduction 
for the resistance of our working apparatus, multiplied by 
the number of parts of the tunnel (a) thus: w=i' — r. Xa. 

This equation, however, gives us the sum of chemical 
actions in the whole series of batteries and decomposition 
troughs, or, in other words, the sum of the actions evinced 
in each ; we generally, however, are desirous of estimating 
the amount done in one particular cell, in which case we divide 
our equation by the number of cells and troughs (11) thus, 

, i'— r X a. 

w' = 

n 

It is at this point where our theory of the pile joins Ohm's 

5* 



74 



THE AMOUNT OF WORK 



law, for virtually, his electromotive power e is equal to our 
i a, or intensity and quantity combined. According to Ohm, 
w, or the work in any battery, is equal to e divided by its 
resistances, and according to our formula w is equal to e— the 
deductions for these- resistances, both of which expressions 
amount to the same thing. The theory here propounded, 
therefore, amounts rather to an analysis of Ohm's formula in 
the battery itself than to an opposition to it, as has been sup- 
posed by some of my mathematico-electrical friends. The 
formulae which are here detailed, appertain to the quality of 
the force produced, and its mode of production, whilst Ohm's 
equation refers to the application when produced. 

Sometimes this equation is rendered extremely complex 
by an increase of the circuit at one side but not at another ; 
in fact, the tunnel is cut jp- ^ 

away on one side, and 
this is a case that is per- 
petually occurring in 
practice. In this case it 
is not impossible but that 
the force is only derived 
from those parts of the 

circuit which are complete ; in that case the equation would 
1 — b x a— p p standing for the incomplete parts. 




be w: 



n 



In this view of the question we are supported by the analogy 
of water running through a pipe of given dimensions from 
a cistern, for however large this cistern be, provided there 
be no more pressure, the water running through the pipe 
would be the same. So far as the voltaic fluid is concerned 
I feel certain, from numerous observations, that beyond a 
certain point the increase of a battery does not cause a 
greater amount of electricity to pass through a given resist- 
ance ; and, perhaps, in those cases, where the enlargement of 
a battery increases the voltaic force, the battery in the former 



IN A GIVEN TIME. 75 

instance was deficient in size in relation to the size of the 
re^sting part r, the tunnel, in fact, having been defective 
originally in that part. It is possible that the expression 
for this condition might be altered : for r, the deduction for 
resistance to the single voltaic circle, might possibly vary in 
some new manner, for which further experiments are wanted. 

In that case it would be w= - The old English ft 

n 

standing for the deductions for the new resistance afforded 
to the whole current. The tunnel might be cut away at 
any other part besides (r) ; thus it might be deficient at (f), 
(a), (c), (r), or (e) ; but the student will readily perceive 
the expressions for these cases. Whilst experimenting upon 
large masses of water or rivers, I have been much astonished 
at the small resistance offered from great lengths of the in- 
terposed fluid, which favours the above supposition. It may 
possibly turn out that (c) and (r) in conducting bodies do 
not affect the (i) but only the (a), but my own opinion 
inclines to the opposite belief. 

Sometimes w is very small, as in De Luc's columns, where 
the total amount of chemical action, although (n) is frequently 
500 to 1000, is so small that the experimenters have even 
denied its existence ; but when we consider that these very 
persons assert, that as soon as chemical action does become 
decidedly manifest, the action ceases, how strongly do they 
favour our views, for, according to our equation, we expect 
(a) to be gradually increased till all action would be stopped, 
w indeed, according to our equation, might be so small, as 
not to be cognizable to our senses for weeks, months, years, 
or centuries; and yet multiplied by a very large (w) would 
show enormous intensity or power of overcoming resistances. 

The present modifications of the theory of galvanism are 
perfectly consonant with every practical direction given in 
the following pages, and the only difference in the theory 
will be found in the uncertainty expressed upon the contact 



76 VOLTAIC AND OTHER ELECTRICITIES. 

and chemical action theories, By removing the slight diffi- 
culties which appeared to envelope the latter theory, by 
showing the necessity for a negative pole to cause power is 
unfounded, the beautiful doctrine of Faraday is placed on 
the surest foundation, and the extraordinary and dogmatical 
paradox of a power without a cause is proved to be a fanciful 
chimera. 

With regard to the connexion of the voltaic power with 
that of electricity produced from other sources, perhaps it 
might be expected I should say a few words. In the voltaic 
battery (i) is small, but may be increased to any size by (n), 
and as we have the power of increasing (a) also unlimitedly, 
we can perform any amount of work per second, indeed we 
might throw down hundreds of tons of copper per second, 
if we were disposed to make our circuit large enough. In 
frictional electricity (i) is enormous, but (a) is depressed to 
its utmost limit, so that not having a perfect command over 
(a) to increase it indefinitely, we cannot at present obtain 
what work we please in a given time. In animal electricity 
(i) is great, (a) is moderately largo. In thermo-electricity 
(i) is depressed, perhaps increasingly, so that although (a) 
and (n) may be multiplied indefinitely, yet, practically, we 
should never be able thoroughly to overcome the smallness 
of (i). In that mighty operation of Nature which has just 
occurred, where the noise accompanying the discharge of 
the electricity over the metropolis was so awful as to alarm 
not only delicate females*, but the stoutest hearts of men, 
and even the heretofore un terrified nervous system of infants 
— in that terrific storm, when every living creature trembled, 
and Nature seemed almost alarmed at her own operations, 
how vast was (i) ! how large (a) ! O ! therefore that I could 

* A violent thunder-storm which visited the metropolis in the year 
1842, at about five o'clock in the morning, and during which a number of 
trees, buildings, churches, &c, over an area of many miles were apparently 
struck at the same instant. 



RESISTANCES OF THE VOLTAIC FORCE. 77 

out have imprisoned that collection of force which in dis- 
charging itself committed such devastation on houses, 
churches, and trees, and, having encased it, been able to 
have let it loose as it might have been required ; then indeed 
would all batteries be henceforth discarded as playthings for 
children — philosophical toys to be admired, still despised, 
for (i a) being unlimitedly great, we could obtain what work 
we pleased in any given time, at no expense. 

The estimate of the parts of (i) in other cases where force 
is produced, i. e. an electricity not proved to be derived from 
chemical action, I do not deem it my business now to con- 
sider, but great difficulties would attend its accurate inves- 
tigation, as it is almost impossible to magnify the size of the 
circle in these cases, in such a way as to make the action in 
each part cognizable by our senses. It is however quite 
evident that as in the voltaic and thermo circuits (i) may be 
magnified to any extent by (n), that the power of (i) in every 
case might be brought to the same standard in the power 
overcoming the resistances r' r 7/ r /7/ &c. 

The obstacles to the completion of the voltaic circuit (o), 
are made up as we have seen of several parts, cr, e, r, c ; but, 
although they differ in kind, still if they have similar resist- 
ing properties, a perfect table might be made, referring 
them to one given standard, showing the separate value of 
each. The principle on which it should be constructed is 
the law of the completion of the voltaic current, which will 
be detailed when treating of the reduction of alloys ; and as 
soon as we have this table accurately and numerically drawn 
up, the principles of the passage of the voltaic circuit, which 
formerly puzzled the most enlightened experimenters, will be 
rendered certain, and the difficulties will be also reduced to 
the facility and certainty of common arithmetic. Having 
obtained perfect tables of (o) and its" several parts, we can 
readily obtain the relative value of (i), derived from various 
sources, by rinding out what extent of (o) neutralizes each 



.* 



78 RESISTANCES TO THE VOLTAIC FORCE. 

individual (i), and the value of (i), or the force of any 
battery will be determined with equal facility. Complete 
tables of (o) and (i) now become the greatest desiderata not 
only to Electro-metallurgists, but to all who use the voltaic 
battery. In attempting to construct tables of (o) as the 
relative power of (o) varies with different amounts of (i), that 
fact must be carefully considered, but probably in many of 
these cases Ohm's law may come to our assistance. 

I now bid adieu to my theory of galvanism and my for- 
mulae ; and to those who have neither time nor inclination to 
dive into these mysteries, remember, in all operations that 
the sum of the deductions for resistance does not exceed the 
sum of the intensities ; and that in increasing the circuit, 
every part is equally enlarged. To those who have devoted 
themselves to these properties, remember, they will be useless 
if not brought into active operation ; thus, if any difficulty 
occurs in your voltaic circuit, refer it at once to its proper 
head, and the operator may be sure that a continual practice 
and habit of using these expressions will enable him to con- 
duct his proceedings with a certainty never obtainable by 
blind experiment. 

Let us now recapitulate every circumstance which, by 
affording a resistance to the passage of the galvanic fluid, will 
lessen the amount of the action. In the first place, in the 
battery itself, the current of electricity might be diminished 
by the metallic plates being too thin to carry the current 
readily. It may also be lessened by the plates being far 
apart, or the interposed liquid being an imperfect conductor. 
The negative metal may be covered with hydrogen and 
rendered nearly inert, or the positive may be rendered inope- 
rative, by the saturation of the acid by the zinc, or the liquid 
by the metallic salt. External to the battery resistance may 
be afforded by small wires, or by connexions of imperfect 
conducting power, or by attaching it to a decomposition ap- 



APPLICATION OF VOLTAIC POWER TO THE ARTS. 79 

paratus, every part of the construction of which obeys the 
same laws as the galvanic battery itself. 

The application of voltaic power to the arts is one of the 
greatest improvements of modern times, and although much 
has been done in this important and extensive field of in- 
quiry, yet this alone suffices to show, that as we progress the 
path to be pursued widens and enlarges, exposing to view an 
immense tract, fertile exactly in proportion to the labour and 
ability employed in its cultivation. 



80 



CHAP. III. 



ON ADDITIONAL SOURCES OF VOLTAIC POWER. 

On hydro, animal, and lightning-electricity, considered as a source of 
power, 104. Magneto-electricity, 105. 

(104.) Whenever electricity, from whatever source it is 
derived, acts upon, or passes through a fluid, the effects 
which are observed are obedient to the same laws. Practi- 
cally, the electricity developed in a voltaic battery is, as a 
general rule, alone applicable to electro-metallurgy ; yet the 
very lightning from the clouds, the electricity from the hydro- 
electric machine, or magneto-electricity, might be, at times, 
applied to the same results. 

With regard to hydro-electricity, a very powerful cur- 



rent may be produced 
by high-pressure steam. 
For this purpose a 
high pressure boiler is 
used, and the steam, 
with aqueous particles, 
passes through a tube, 
and by their friction 
against a piece of hard 
wood the electric force 
is generated. At pre- 
sent it has not been 
employed for electro- 
metallurgy, and is pro- 
bably vastly inferior to 
the voltaic battery. 



Fig. 18. 




ELECTRO-MAGNETIC CURRENTS. . 81 

Gassiot, by way perhaps of a humorous experiment, 
made an electric eel form one. of Nobile's rings ; but it is 
nardly necessary to state, that, for electro-metallurgic opera- 
tions, we cannot ordinarily press these curious creatures 
into our service. 

There is something truly poetical in the idea of making 
lightning our servant instead of our master ; but as it has 
decomposed water, it could also be made to perform some 
electro-metallurgic process : and thus we may safely say that 
the matter of fact of the present day exceeds, in poetical 
idea, the wildest imaginations of former ages. That which 
in a former age would be so far beyond the sublime as to 
constitute the ridiculous, now becomes an ordinary matter 
of fact, not even presenting a subject for observation. 

By the electro-magnetic contrivances, we have the power 
of obtaining a current of intensity from a current of quantity. 
It was first discovered by Faraday, that, upon making or 
breaking the contact of a galvanic battery by a long wire, 
another current was developed in a second wire, isolated 
from the first by some non-conducting material. Thus, if 
we take a copper wire, say 60 feet long and one eighth of an 
inch thick, and form it into a helix by winding it regularly 
round a hollow tube, and superimpose upon that a great 
length (say 1200 feet) of a very thin wire, covered with silk, 
cotton, or any such non-conducting material, and wound 
round the first wire in a similar direction, we form an appa- 
ratus that at once shows the experiment on making contact 
with the two ends of the thick wire with the plates of a gal- 
vanic battery. A current of electricity is generated in the 
second wire ; and though the first current may be derived 
from only a single pair of plates, the second current may 
have amazing intensity, in fact, sufficient to give the most 
powerful shocks ; a secondary current is produced on again 
breaking contact, but no second current is formed whilst the 
circuit is completed. These effects are far more exalted 



82 



ELECTRO-MAGNETIC APPARATUS. 



if we place a piece of soft iron, or a bundle of soft iron 
wires, into the tube round which the primary wire is wound, 
because we then add the powers of magnetic induction to 
that derived directly from the galvanic battery. A machine 
upon this principle is constructed in the manner above de- 
tailed, one end of the primary wire being connected, to a 
metallic-toothed wheel, the other joining a flexible piece of 
brass capable of pressing the teeth. By revolving the 
wheel the contact is made and broken, according to the 
rapidity of the revolution, and thus hundreds of shocks may 
be transmitted in a minute. 

The induced current so produced is a to and fro current ; 
but the current should always be cut off (fig. 19.). Messrs. 
Home and Thornthwaite have devised a self-acting machine, 
which they call an electro-magnetic machine, in which the 
secondary current is cut off, from the peculiarity of its con- 

Fig. 19. 




struction. In these cases the magnetic induction is added 
to the galvanic induction, and the result may be beneficially 
used in one or two instances for the purposes of the arts. 






ELECTRO-MAGNETIC APPARATUS. 83 

(105.) Fifteen years ago my much respected master, Pro- 
fessor Daniell, used to show in his lectures a magnet, from 
which Faraday first obtained an electric spark by induction. 
When, with darkened windows he used to demonstrate this 
little spark, nothing could exceed his animation and delight 
that his magnet was that on which the discovery was made. 
He little thought then, that that little philosopher's spark, in a 
few short years, would find its way into the arts, and consti- 
tute a source of wealth to the manufacturers, and a source of 
honour to the inventor. The philosopher's spark has been 
converted into a working electric current, by using very 
powerful magnets, and revolving before them pieces of soft 
iron wound round with numerous layers of silk ; according to 
the power of the magnet, the closeness of the approximation 
of the armatures, and the length and sizes of the wires, so do 
we obtain a greater or less intensity or quantity of electricity 
by the revolution of the armatures (fig. 19). The magneto- 
electric apparatus gives a to and fro current ; but for electro- 
metallurgic processes, it may be readily contrived that 
every alternate current may be cut orT. It is a curious fact, 
that, although this machine gives an intermittent current, it 
causes a constant deflection of a magnetic needle, so that, in 
its chemical effects, it is equivalent to a constant current. 

Throwing out of consideration the first cost of a magneto- 
electric machine, we may consider whether it be preferable 
to the battery as a source of power. It is a primary law of 
physics that to produce any change of matter a corresponding 
change of matter must take place, and in the battery the 
change of matter takes place in the battery cell, where 
the power arises from the action of the zinc on the 
water. In the magneto-electric machine, the power arises 
from the combustion of the coals which generates the steam 
which moves the wheels of the steam-engine and turns the 
armatures. As wherever there is a steam-engine, the power 
usually exceeds the demand, it may be thought that magneto- 



84 



MAGNETO-ELECTRIC TELEGRAPH. 



electricity is obtained for nothing. Nevertheless, although 
magneto-electricity has been beneficially applied to the 
reduction of gold and silver, both of which, from their high 
equivalents, require but a low amount of electricity to effect 
any required reduction, I am of opinion that the* battery 
must, for the present, supersede the magneto-electric power. 

Fig. 20. 




Mr. Henley has patented a magneto-electric telegraph, 
which certainly appears to be the most elegant and perfect 
instrument of that kind which has yet been devised. 

The American papers have lately contained an account of 
the manufacture of gas by this machine ; but the published 
statements contain internal evidence of the whole paragraph 
being an attempt at a circumstantial hoax, such as the 
Americans alone can produce. 

The magneto-electric machine, however, deserves grave 



MAGNETO-ELECTRIC MACHINES. 85 

consideration and attention; for if ever its construction 
should be so improved, that water could be readily decom- 
posed in large quantities by its agency, then indeed it would 
be one of the most important engines of modern invention. 

When electricity has been obtained from the magneto- 
electric machine it differs not from electricity derived from 
battery ; and when it acts upon any metallic or other solution 
or fluid, the effects produced depend upon the intensity or 
quantity of the electricity actually passing through the fluid. 
The principal disadvantage of these machines is the produc- 
tion of a power having but feeble quantity, although it ex- 
hibits a very high intensity. As a consequence of the high 
intensity we are enabled by its means to overcome great re- 
sistance. Hence iit its economical application the compound 
trough hereafter to be described may be employed. 



86 






BOOK THE SECOND. 

ON ELECTRO-METALLURGY. 
CHAPTER I. 

ON THE APPARATUS TO BE EMPLOYED FOR THE REDUCTION 

OF THE METALS. 

The idea of electro-metallurgy, suggested by Daniell's battery, 106. The 
porous tube or single cell apparatus, 106 — 112. Capillary tube appa- 
ratus, 113. Plaster apparatus, zinc, iron, and tin positive poles, 114. 
Compound battery apparatus, 115, 116. Single battery apparatus, 11*7, 
118. Precipitating trough, 119. Single cell and battery conjoined, 
120. Mason's arrangement, 121. Management of the apparatus, 122, 
123. Lines on the reduced metal, how to be avoided, 124. Adhesion 
and non-adhesion of the reduced metal to its mould, 125 — 128. Appa- 
rent adhesion, 128. Lateral growth of the reduced metal, 129. Rela- 
tive expense of various modes of the reduction of metals. 

(106.) Electro-Metallurgy, depending essentially on elec- 
tric agency, is subject to the operation of the same prin- 
ciples, and governed by the same laws which have already 
been laid down in the book which treats of galvanism and 
galvanic batteries. The successful reduction therefore of the 
metals must depend entirely upon a thorough knowledge of 
galvanism and galvanic apparatus. We should recommend 
our readers, then, before they enter upon this department, to 
make themselves thoroughly conversant with the contents 
of the first book ; for what operation can be successfully per- 
formed without a complete knowledge of the nature of the 
implements with which that operation is to be effected. 



POROUS DIAPHRAGMS. 87 

Independently, however, of these general galvanic pro- 
perties already adverted to, there are certain particular ones 
appertaining either to the different metals, or to the dif- 
ferent qualities of the same metals, which have to be con- 
sidered in detail, as well as the apparatus to be employed for 
precipitations. 

The idea of electro-metallurgy appears to have been first 
suggested by the use of Professor Darnell's battery, for 
during its action the outer copper vessel, which is the nega- 
tive metal, becomes coated with an additional layer of me- 
tallic copper ; hence, as this new deposit is placed in close 
apposition to the vessel, a cast is produced. If we call to 
mind the construction of the battery, we see that it consists 
essentially of two vessels, the inner being porous, and con- 
taining dilute sulphuric acid, while the outer contains the 
solution of sulphate of copper, and the negative metal. 

Daniell's battery is composed of two vessels in which two 
separate processes are going on ; in one, the solution of the 
zinc, in the other, the reduction of the metal from the solu- 
tion. In many cases the passage of the sulphate of zinc 
formed during the action into the other cell is not of much 
consequence ; but when we are desirous of completely sepa- 
rating the two fluids, we use a diaphragm capable of effect- 
ing that object. 

(107.) The substance best adapted to complete the separa- 
tion of the solutions, in a single cell apparatus, is animal mem- 
brane. Of this there are various kinds : bladders of different 
textures, the lining membrane of the intestine of the ox, fine 
gold-beater's skin, or bladders of various animals, may be 
used according to circumstances. Animal membrane sepa- 
rates solutions better than any other diaphragm, but for most 
purposes, it affords too much resistance to the passage of the 
current. There are a great variety ef papers which may be 
used for porous tubes : they admit the current according to 
their relative textures. Brown paper and cartridge paper 



88 SINGLE CELL APPARATUS. 

are frequently of value for the electro-metallurgist, and they 
last for a considerable period without renewal. Of late, 
earthenware tubes have been very extensively employed. 
The kind of most value are made absorbent, similar to the 
vessels employed for wine-coolers, and are made of different 
shapes, to suit various purposes. The best are generally 
made with care, and of superior clay ; but the common earthen- 
ware garden-pots answer in some cases where porous vessels 
are required. In selecting a porous vessel we have to guard 
against two extremes ; for, either it may be over fired or 
baked at too great a heat, when it will not be sufficiently 
permeable by liquids, or it may not be sufficiently baked, when 
any metallic solution will act upon and partly dissolve its 
substance. We should, furthermore, always ascertain whether 
water will pass slowly, but entirely, through every part of 
its texture, in order that universal porosity may be proved. 
But the practised electro-metallurgist can always judge of 
the fact by touching it with his tongue, when the degree of 
dryness produced on that organ by the absorption of its 
moisture will indicate the freedom with which liquids will 
pass. A clayey appearance, and peculiar odour when placed 
in water, are the only test of an imperfect baking. A com- 
mon tobacco pipe, with the hole blocked up with a little plug 
of wood, is very useful for small experiments. Wooden porous 
tubes have been used by some persons ; Jacobi makes mention 
of having employed them. They should always be boiled in 
acid before they are first used, to render them more porous ; 
but no particular advantage attends their application. Plaster 
of Paris is sometimes employed, but it speedily becomes acted 
upon by the fluids, and upon the whole is not a useful dia- 
phragm. Any vessel with a small fissure, or fine crack, in it 
may be used as a porous pot, for any vessel which will let 
fluid run out, will allow the galvanic current to pass. We 
have already mentioned, in a former part of the work, that 
the more porous this vessel is, the greater the quantity of 



SINGLE CELL APPARATUS, 



89 



electricity developed, and the greater, therefore, the quan- 
tity of metal deposited, as the amount of deposit is always 
in relation to the quantity of electricity generated. The 
following is the order in which different substances stand 
with regard to their capabilities of admitting the passage of 
electricity : — 

Brown paper, 
Thin plaster of Paris, 
Porous earthenware, 
Gold beaters' skin, 
Bladders of various thickness, 
Thick plaster of Paris, 
Capillary tube. 

(108.) Of the various forms of apparatus, which may be 
used for the precipitation of the metals, the most simple is 
Daniell's battery, having a porous earthenware tube, to con- 
tain the acid and zinc, whilst the negative metal, which is 
usually a mould, is placed externally to this, and connected 
by a piece of wire to the zinc. Thus, for instance, take a 
pound pot, and half fill it with a solution of sulphate of cop- 
per (s) ; in this, place the earthen ves- 
sel (p), with the dilute acid (a) and 
zinc (z), and this constitutes the whole 
of the present form of apparatus ; for, 
when we desire to make an electro- 
medallion, it is only necessary to place 
one or more casts in the outer vessel 
(m ni) connected by a wire with the 
zinc, and then action will immediately 
commence. Anv number of moulds 
may be placed in the outer vessel, pro- 
vided they can radiate to the zinc. Saturation of the liquid 
may be preserved by suspending some of the salt in a linen 
bag over the mould. This form is objectionable, because 

6 




90 



SINGLE CELL APPARATUS. 



the salt of zinc speedily passes through to the outer vessel • 
but it has the advantage of allowing the mould to be placed 
vertically, in which position it is much less liable to have 
particles of dust settling upon it. There is no limit to the 
size of this outer vessel : for a water-butt, a tank, or even a 
lake naturally impregnated with sulphate of copper, would 
form glorious apparatus for the electro-metallurgist. 

(J 09.) There is another form where bladder takes the place 
of the earthen vessel, and where the position of the cast is 
horizontal. Here, the outer vessel, which is square, is made 
of wood, coated internally with cement ; on one part of the 
edge of which, a piece of 
brass is fixed, in which are 
two holes, one for connec- 
tion with the wire of the 
cast, the other with that of 
the zinc. In the interior of 
the trough, a moveable shelf 
of mahogany is placed, on 
which is supported a glass 
containing a zinc plate, and crystals of sulphate of copper to 
be dissolved. The glass has a piece of bladder tied over the 
rim, and this forms an outer vessel similar to the porous tube 
in the former apparatus. It, in like manner, contains the 
acid and zinc ; the latter being connected by a screw to a 
wire, in such a way that it can be readily removed. This 
apparatus is preferable in many respects to that first de- 
scribed ; because the sulphate of zinc cannot pass through the 
membrane readily to the copper, and facilities are offered for 
changing the zinc and acids, &c. In this apparatus, care 
must be taken that the mouth of the glass be wide enough to 
afford a radiating point from the zinc to every part of the 
cast, as it has been already noticed, that want of attention to 
this would be attended with inconvenience. (17.) 

(110.) In every single cell apparatus, the solution of me- 




SINGLE CELL APPARATUS. 91 

tallic salt should be maintained in the required degree of 
concentration, by keeping some crystals of the salt undis- 
solved in the solution. If these crystals are allowed to sink 
to the bottom of the vessel, they will not answer the intended 
purpose of maintaining a saturated solution ; for the portions 
of the fluid which have been deprived of their metallic salt 
rise to the surface, whilst the saturated parts remain in 
contact with the crystals at the bottom, thus preventing 
their solution. This difficulty may, however, be readily 
overcome, by placing the crystals to be dissolved in a little 
bag, on a shelf at the top of the liquid, by which means the - 
saturation of the fluid will be ensured. 

(111.) Another form might be made by dividing a box 
into two compartments, by a flat porous slab of earthenware, 
similar in composition to the porous tubes of a Daniell's bat- 
tery. Into one compartment the solution of sulphate of 
copper is to be put, together with the negative metal, which 
in the cut is represented by two moulds (m m), and into 
the other dilute sulphuric acid Fig. 23. 

(a) and the zinc (z). The ad- 
vantage of this apparatus would 
consist in the facility gained in 
the manipulation ; and in the 
arrangement of the positive and 
negative metals, so that! hey may 
be at every place equidistant 

from each other — a circumstance of great importance. The 
porous diaphragm, however, cannot be made of any large 
size, so, perhaps, it might be exchanged for a more ready, 
but less durable one of plaster of Paris, paper, or bladder. 
The decomposition apparatus (fig. 11.) made of a cut tumbler 
answers well for numerous experiments. 

(112.) Other forms may suggest themselves to the 
operator, for in whatever way a Daniell's battery may be 
constructed, a similar form will equally answer for the 




92 



CAPILLARY TUBE APPARATUS. 



electro-metallurgist. (38.) The only circumstance to be 
observed is, that the zinc be equidistant at every place from 
the metal on which the reduction of the new metal is to be 
effected, so that the deposit may be everywhere equally 
thick. If the distance varies, the reduced metal will be 
found to be of unequal thickness; that part nearest the 
positive metal will be very thick, whilst the substance will 
diminish as it recedes from that point : in some cases the 
effect is more apparent than in others, but occasionally, where 
a mere rod of positive metal is placed opposite a large sur- 
face of negative, a complete convex mass is formed, gra- 
dually diminishing in thickness in every direction. In some 
cases these effects of radiation present some complex pheno- 
mena ; but generally they may be referred to the fact, that the 
galvanic principle is not so essentially radiant, but that it 
will pass round a corner : thus, if a flat piece of copper is 
placed opposite to another mould in a solution of sulphate of 
copper, a portion of current is generated at every part of 
the back of the positive pole, which, turning round the corner, 
causes a far greater mass of metal to be reduced at the cir- 
cumference of the mould. At other times the effects of 
radiation are farther complicated by the imperfect uniformity 
of the strength of the solution during the action of the ap- 
paratus, in which case, every part not being of equal con- 
ducting power will admit a different 'quantity of electricity, 
and, therefore, a different thickness of metal will be reduced. 
(113.) An apparatus for very weak currents, I sometimes 
use with great advantage, when the change takes place at 
the cathode of the battery. It is made in a very simple 
manner: the solution to be decomposed is placed in a 
tumbler ; a piece of glass tube is then drawn at one extre- 
mity to a capillary bore. This fulfils the office of the porous 
tube, and contains the zinc (which in this arrangement is 
merely a piece of amalgamated zinc wire) and a very dilute 
acid solution. The quantity of electricity generated by such 



ZINC POSITIVE POLE. 93 

an arrangement as this, is necessarily very small indeed, for 
the construction is in every way unfavourable to its develop- 
ment ; first, the diluteness of the acid solution materially 
lessens the quantity ; then, the hole through which the cur- 
rent has to pass is so small that much force is required to 
blow any liquid through the aperture, even by drops, and 
therefore a great impediment is offered to the passage of the 
current. Moreover, a very fine platinum wire is employed 
to effect communication; and lastly, the substance, which 
is the subject of experiment, is not placed opposite to the 
capillary hole. The mode in which the capillary tube acts in 
lessening the current, seems to be by interrupting or break- 
ing the continuity of the fluids, so that but a feeble amount 
of the current can pass. The regulation of the quantity of 
electricity can be perfectly effected by regulating the bore of 
the tube. 

(114.) Sometimes, when a very feeble current is required, 
a glass is filled up at one end with a thick piece of plaster, 
which fulfils the office of a porous tube. Where we only re- 
quire to lessen slightly the quantity of electricity, we con- 
tent ourselves with extending the distance between the elec- 
tro-positive and negative metals. In other cases we use 
a thick bladder or thin communicating wires, and we con- 
join the whole or a part of these contrivances for lessening 
the power. 

In the single cell apparatus up to the present time, zinc 
has 7 been invariably used for the positive metal, and various 
solutions may be employed with the zinc : common salt has 
been much used, &c. The various sulphates and other neu- 
tral salts can be also employed without the amalgamation 
of the zinc ; but if we go to the expense of this amalgama- 
tion, we may employ dilute sulphuric acid, or dilute muriatic 
acid, both of which, from their superior conducting power, 
enable us to reduce far more metal in a given time. Zinc in 



94 IRON SINGLE CELL APPARATUS. 

a single cell will reduce nearly all the metals, and, as it 
forms soluble salts with nitric, muriatic, sulphuric, acetic, 
tartaric acids, it may, therefore, be employed for all salts 
which contain these acids, for we must never forget that it is 
essential that the new salt formed should be soluble in water, 
and that a sufficiency of water be supplied for its solution. 

Now having discussed the arrangements principally suit- 
able to those cases where zinc is employed as the positive 
metal, or metal used to generate the current, I have to im- 
part the great secret, that it is not always necessary to use 
zinc as the generator of the voltaic power, for, practically, 
it is possible in a great many cases, especially in the reduc- 
tion of copper, to make iron take the place of zinc, thereby 
superseding the use of that expensive metal, and substi- 
tuting one of but trifling value. But iron is not capable of 
imparting the same electro-motive power, intensity or prim- 
itive force of the galvanic principle that zinc is so eminently 
endowed with ; for this reason we are compelled to use a 
greater extent of surface when iron is employed, and from 
this cause up to the present day has been but little or never 
employed. Moreover, we have still other difficulties *to con- 
tend with ; iron cannot be amalgamated like zinc to stop local 
action, and, therefore, can only be used profitably with saline 
or other solutions that do not themselves act upon the iron 
when not forming a galvanic current. The apparatus the 
most suitable to the application of this metal is that which 
most favours an increase of the positive metal. A very simple 
form is a common cast-iron supply cistern, into whicn a 
parallelopiped porous tube, one inch smaller each way, might 
be placed, separated by two pieces of wood inserted at the 
bottom of the tank. The inner vessel contains the satu- 
rated solution of sulphate of copper, with crystals suspended 
at the upper part to maintain the saturation of the fluid, and 
its conducting power should be increased as much as possible 



IRON SINGLE CELL APPARATUS. 95 

by the addition of dilute acid. Before we determine what is 
the best exciting fluid to- be used in the iron cell, we must 
determine what salt of iron is most desirable to be formed 
during the action of our apparatus. Iron forms soluble salts, 
with a considerable variety of acids, with muriatic, nitric, and 
sulphuric, &c. ; but I am inclined to believe, from my experi- 
ments, that the sulphate is the most convenient salt to be 
generated ; therefore, we must employ a solution of some sul- 
phate, of which the sulphate of zinc, sulphate of soda, or what 
is, perhaps, best, sulphate of magnesia, or Epsom salts. This 
salt is retailed by chemists for about one penny an ounce ; 
but the electro-metallurgist will find that he will be enabled to 
buy a pound for about two pence. I have tried a great 
variety of other saline substances in the outer cell, as nitrates, 
chlorides ; but, upon the whole, the sulphates appear to be en- 
titled to the preference. The low combining number of iron 
adds much to its advantage, for twenty-eight grains would 
be as effective, that is, would generate as much power, 
as thirty-two grains of zinc. By using an iron positive pole, 
I feel no doubt that many who have never succeeded in 
making electro-medallions heretofore, will be enabled to 
carry on their operations, although slowly, yet with perfect 
success. A box, divided by a porous diaphragm, and every 
other single cell apparatus in which we can place a large 
surface of metal, is suitable for the application of iron as the 
positive metal. It is really very pretty to pick up a few old 
rusty nails, and from them generate a sufficiency of the ex- 
traordinary and mysterious power of galvanism to make a 
copy, by a few minutes' labour and a few hours' patience, 
of the most elaborate work of art that the exalted imagina- 
tion and the untiring patience of the ancient Grecian could 
possibly execute. When we can obtain an accurate cast of 
a Syracusan coin, worth upwards of one hundred pounds, 
by two or three old rusty nails, and the solution of a penny- 



96 LEAD POSITIVE POLE. 

piece, let no one henceforward throw away or despise an 
old rusty nail.* 

There are other metals besides zinc and iron that might 
be used to generate electricity : thus, lead will reduce 
copper, silver, gold, and various other metals. When it is 
employed for electro-metallurgical experiments we must 
form a soluble salt, of which the acetate and nitrate are 
most conspicuous. If we use nitrate of potash, in the 
outer side with the lead, and a solution of metallic salt, 
say of copper, in the inner side, wdth the negative plate, 
the reduction will take place. It is vain to attempt to 
reduce a sulphate by this salt, for the sulphate of lead is 
absolutely insoluble. Its equivalent number is very high, 
one hundred and four of lead being equal to thirty-two of 
zinc, which is one serious objection to its use. The only 
chance of its ever being employed for the reduction of 
any metal, especially copper, is the possibility of the 
nitrate of lead, formed during the galvanic action, being a 
valuable product ; for were this the case, we should obtain 
our power for nothing, and the cost to the electro-metal- 
lurgist would be only the value of the weight of metal pro- 
duced, plus the cost of the previous process, for converting 
it into a metallic salt. The sulphate of iron and sulphate 
of zinc produced in the former cases are now thrown away ; 
but, as in many chemical manufactures the cost depends on 
the value of the products, it would be desirable for the elec- 

* Since writing the above, I perceived the following paragraph in 
" The Chemist " for this month, by Mr. Z. J. Rockline, which I subjoin 
entire : — " In all my electrotype experiments I have employed, and with 
the greatest success, ordinary sheet-iron, instead of zinc, for the positive 
metal, — than which it is much cheaper. The difference must, I think, 
be palpable in large electro-castings, where extensive surfaces of zinc 
would be necessarily requisite. Iron, in the form of cylindrical rods, 
which are extensively manufactured, would, if cut into suitable lengths, 
form most excellent and cheap substitutes for the zinc bars hitherto used 
in circular constant batteries. To electrotypists, this metal, in whatever 
form it may be used, must prove a cheap substitute for zinc." 



TIN POSITIVE POLE. 97 

tro-metallurgist to form a salt which is of value. I throw 
out this hint for trial, as I have reduced copper from its 
nitrate by lead, so, if the nitrate of lead could be converted 
into the carbonate with advantage, we should obtain our 
power comparatively for nothing : lead gives a feeble electro- 
motive power ; therefore, it requires a large plate, and a thin 
porous tube. I hear of no instance where lead has ever been 
practically used in the arts for this purpose. 

Tin may be used to generate electricity, it being soluble in 
muriatic, sulphuric, acetic, oxalic acids, &c. It has a feeble 
force, requires a large plate, and a thin porous tube. It is 
best used with dilute sulphuric acid on on** side, and the me- 
tallic salt, which should be a sulphate, on the other. It re- 
duces several metals, but, unfortunately, has a high combining 
number, requiring fifty- eight grains to generate as much 
power as thirty -two grains of zinc. Some alloys of tin and 
zinc might come into use for the single cell apparatus, did 
not the high equivalent and price of tin prohibit its 
adoption. 

Other metals might be used, under certain circumstances, 
as the positive metal to generate power : for instance, copper 
to reduce palladium, gold, or platinum ; silver to reduce gold 
and platinum ; but, as they will probably never be employed 
by the electro-metallurgist as a positive pole, there can be no 
occasion to consider them farther: always remembering, how- 
ever, that whatever metal is employed as a positive element, 
it is requisite that such an exciting fluid be employed that 
a soluble salt may be generated during the action of the 
apparatus, and that sufficiency of water be supplied to dis- 
solve it as soon as formed. 

(115.) In all these cases the metals are precipitated at the 
negative metal of a single battery. In like manner, by what- 
ever other method we can render a plate negative, there will 
the metal be precipitated ; thus, if a battery, sufficient to 
decompose acidulated water, be connected with two platinum 

6* 



98 BATTERY APPARATUS. 

poles, at one pole oxygen, at the other hydrogen, will be 
evolved ; therefore, at the latter the metal would be precipi- 
tated. It has been mentioned before, that one cell of Grove's, 
two or three of Daniell's, or of my form of battery, will de- 
compose acidulated water between platinum poles ; but still, 
with that series only, a feeble quantity of gas is given oft 
Now where we wish to employ feeble currents, the series 
just mentioned may be used with great advantage. 

(116.) Where we have considerable resistance to overcome, 
and require but very feeble quantity, we may use a number 
of cells, exciting the battery either by simple water, or water 
acidulated with a single drop of acid in each cell. The 
oxygen in this method of reducing the metals is always 
evolved at the positive pole, and the acid in combination 
with the metal set free, so that the solution gradually becomes 
more acid. In most cases, however, we require to precipitate 
a large quantity of metal, and then it becomes a matter of 
importance to effect that object by the smallest series, as by 
this compound battery apparatus the cost is multiplied by a 
number of cells employed. 

(117.) For most purposes the last method is very seldom 
adopted; but advantage is taken of the affinity which most 
metals have for the oxygen ; and instead of using a platinum 
pole at the oxygen end of the battery, which affords great re- 
sistance to the passage of the galvanic fluid, we employ a piece 
of metal of the same nature as that which we wish to precipi- 
tate, which performs the functions of the positive plate or 
zincode in the trough. As the solution of metallic salt is 
continually depositing its metal, the piece which constitutes 
the positive pole is dissolved by the acid and oxygen which 
held the reduced metal in solution, and the liquid is thus 
kept nearly at the same point of saturation. One battery is 
amply sufficient for this mode, as there is but little resistance 
to overcome. 

(118.) To illustrate this method, let us suppose that we 



BATTERY APPARATUS. 



99 




have to take a cast in copper. A solution of a salt of copper 
is to be placed in a convenient vessel (b), and the object on 
which the precipitation is to take place (n), is to be connected 
with the zinc (z) of* the battery (a), whilst a piece of sheet 
copper (p) is connected with the silver (s). As soon as 
action commences, water is decomposed, oxygen passes to the 
copper pole and oxydizes it, 
and the hydrogen passes to 
the negative plate. Whilst 
the decomposition is taking 
place, oxide of copper is 
supposed to be passing to 
the ' negative pole, and the 
acid to the positive pole ; 
the hydrogen reduces the 
oxide of copper at the nega- 
tive plate, whilst the acid 
combines with oxide of 
copper at the positive end, 

and thus the saturation is continued. Practically we. never 
find that all the acid passes to the positive pole, but on the 
contrary, the proper diffusion of the metallic salt occasions 
us much inconvenience.* 

A series of precipitating troughs, arranged like a com- 
pound battery, may be employed occasionally with only one 
battery. In this case, we should have one generating cell in 
the battery, and six, eight, or ten decomposition cells ;" there- 
fore, by the fundamental laws to which the action of the 
galvanic fluid is obedient, we should have six, eight, or ten 
equivalents of metal reduced for one equivalent of zinc. 
Theoretically, this apparatus exceeds every other in economy 
—practically, it has not been so much employed as it ought 

* It has been mentioned before (99.), that Professor Daniell has given 
a different theoretical explanation of these decompositions, though, prac- 
tically, the change taking place is the same as here given. 



100 



PRECIPITATING TROUGH. 




to be, particularly in the reduction of plain copper-plates. 
The galvanic series is made by alternating the metal to be 
dissolved (c) with the ™. 25 

object to receive the 
precipitate (m), the 
last mould being join- 
ed to the zinc (z) of 
the battery, and the 
last copper with the 
silver (s) ; the positive 
plates should be large, 
and the liquid ren- 
dered as conducting as 

possible to lessen resistance. It is important in this ap- 
paratus that every positive and negative plate should possess 
nearly the same surface, and the solution the same strength, 
in order that metal of the same quality should be reduced in 
each cell. 

(119.) The apparatus used as a precipitating trough, must 
vary in shape, — round, flat, square, according to the form 
of the object to be copied ; its dimensions may vary from a 
single drop to the largest reservoir filled with metallic solu- 
tion instead of water, and the solution must be altered 
according to the metal to be thrown down. These will de- 
mand a particular description ; but here we must say a few 
words as to the materials best adapted for this vessel, viz., 
the precipitating trough, and, certainly, glass is preferable in 
all respects, excepting its brittleness and its expense ; these 
two qualities rendering it much less generally applicable 
than it would otherwise be. For some metallic solutions it 
is absolutely necessary to employ glass, as other vessels are 
more or less acted upon by them. The removal of the excise 
duty from this commodity will ultimately prove a great boon 
to the chemist ; as he will be enabled to obtain vessels which 
he could never otherwise reasonably hope for. Porcelain of 



PRECIPITATING TROUGH. 101 

some kinds, such as Wedgewood's, &c, is found to be occa- 
sionally useful. However, even this is too expensive, and 
we have recourse sometimes to the common earthenware. 
Doubtless, many will be astonished at being informed that 
most metallic substances, in a state of solution, will penetrate 
through the glazing, into the very heart or biscuit of the jar, 
and freely pass to the exterior of every kind of earthen 
vessel. This can be only thoroughly prevented by coating 
the interior with pitch.. The best ironstone ware was thought 
to be invaluable to the electro-metallurgist, as, if well glazed, 
it was supposed to last for any length of time. A refiner 
showed me some that he had used for parting gold during 
twenty years, as good as new. Whenever round vessels can 
be employed, the electro-metallurgist will be enabled to find 
them ready-made, at the large earthenware houses, as they 
are frequently used as salting vessels. If they could be 
manufactured similar to a trough, they would be of extensive 
application; but the makers complain of their warping in 
the oven. Even with this form of ware, in process of time, 
the metallic salt intrudes and disintegrates them. Wooden 
vessels are more frequently employed than these, because 
they admit of great variety of form, and can be rendered 
completely water-tight, by a cement composed of bees' wax 
one pound, rosin five pounds, red ochre one pound, and two 
table-spoonfuls of plaster of Paris, A common tin trough, 
or especially a leaden vessel, will answer, but the interior 
must, in like manner, be coated either with cement or pitch. 
Leaden vessels are particularly applicable when the metal is 
to be reduced from its sulphate. One advantage of the 
pitch is, that the salt in solution has but little tendency to 
crystallize upon it, which, with other substances, is a very 
troublesome property ; as, occasionally, the whole of the salt 
from a solution will pass to the outer part of the vessel, thus 
covering it with crystals. Slate troughs have also been fre- 
quently used ; they ought always to be painted or pitched, 



102 PRECIPITATING TROUGH. 

to prevent the absorption of the liquid, which is apt to pene- 
trate into the slates, and crystallize and disintegrate the 
substance, which is always made up of numerous layers. 
The sides are generally bolted together with copper ties; 
but slate vessels should altogether be discarded, as they are 
not found to last above a twelvemonth. 

Troughs of a peculiar construction have been employed by 
my friend Mr. Terry ; he obtains two boxes, one so much 
smaller than the other that a space of half an inch is every- 
where left when one is inserted in the other. The interval 
is filled with melted pitch, and the inner one is lined also 
with the same material. He finds that troughs made in this 
way are admirably adapted for the intended purpose, and 
doubtless they might be employed in some cases. 

Within the last few years a new substance of the highest 
possible importance has been introduced into Europe, called 
gutta-percha. It is very similar to Indian-rubber in most 
of its properties, but w r ants its extensibility. It has the 
power of resisting, at moderate temperatures, the action of 
acids and alkalies, if they be not too strong. It is imper- 
vious to moisture, and pieces can be readily joined together 
by moderate heat and pressure. From these invaluable 
qualities, gutta-percha is now extensively used by electro- 
metallurgists to line wooden tanks, and these troughs are 
the best which can be employed for these purposes, and 
are now superseding every other form of trough. I have 
seen troughs in use for two or three years which were as 
perfect at the end as they were in the beginning of their use ; 
and, in fact, gutta-percha should in future be the sheet-anchor 
of electro-metallurgists. 

The galvanic battery and precipitating trough is the pro- 
cess almost universally adopted for all large objects, and there 
are many reasons why it should be employed. In the first 
place, we are enabled to regulate the quantity of electricity 
to the strength of the solution far better than by any other 



BATTERY APPARATUS. 103 

method ; secondly, we are enabled to keep up nearly a uni- 
form strength of solution, and, lastly, the process is frequently 
cheaper. In fact we have two or three manufacturing pro- 
cesses going on at the same time ; we are not only generating 
our electricity and reducing our metal into the form we 
require it, but we are actually forming, by the same opera- 
tion, our sulphate of copper or other salts. To reduce 
metallic copper from crystals of blue vitriol, or silver from 
lunar caustic, may appear to the unlearned to be a sort of 
alchemical operation, whereby copper or silver is actually 
made ; but this is by no means the case, for we only re-obtain 
that metal which we had formerly made into the salt, and 
we have to pay, occasionally, at a most exorbitant rate for 
that change. All this cost we save by making the battery 
our manufacturer, and the trough our laboratory, for by 
using a certain portion of metallic salt in the first instance, 
the metal, during the action of the battery, is reduced, and 
the acid combines with another portion of metal, so that, in 
this way, the acid contained in a few ounces of metallic salt 
may be employed over and over again, as there is no limit 
to the amount of metal that might pass through it. 

The galvanic battery and precipitating trough need not be 
joined together like Siamese twins. They may be separated 
to any distance, provided the conducting wires afford no 
resistance to the passage of the fluid ; therefore, when we 
separate them to any amount we should make our connecting 
rods of copper, which is a good conductor, and take care to 
employ thick rods instead of wire. Sometimes it has been 
found convenient to have our batteries in one room, and our 
troughs in the other. In the first room, everything necessary 
for the galvanic batteries should be kept, such as zinc, acid, 
mercury, connecting wires, &c. &c. In the other room, 
everything should be methodically arranged for the electro- 
metallurgists. If operations were carried on in a very 
extensive scale, and a great variety of metals were being 



104 



MASON S APPARATUS. 



reduced, then would the manufacturer do well to devote a 
separate apartment to each separate metal. I can see in 
my mind's eye a large electro-metallurgical manufactory, 
with the batteries in a room in the centre, surrounded by 
rooms on eyery side, in each of which a different metal is 
being deposited. 

(120.) Another form of apparatus may be employed occa- 
sionally with advantage ; when we require a considerable 
intensity, or power to overcome obstacles, and do not wish to 
incur the expense of a large series. It is a union of the 
single apparatus and the battery. In the decomposition cell 
we have a porous tube, containing the acid and zinc, and in 
the outer part we have the solution to be decomposed. The 
zinc is to be connected with the silver of the battery, and the 
zinc of the battery with the negative plate in the decomposi- 
tion cell, and thus the circuit is completed. It is manifest 
that this apparatus increases the power, by adding one more 
to the series, and thus, by using zinc at the positive pole of 
the decomposition cell, the impediment offered to the electric 
current is prevented. 

(121.) There is yet another mode by which we can preci- 
pitate the metals with the utmost cheapness, though the 
length of time required is very much increased by the process. 
We use here the DanielPs Fig. 26. 

battery apparatus, or single 
cell for the reduction of the 
metal ; but instead of con- 
necting the zinc with the 
negative metal at once, we 
make that zinc and medal a 
battery to be connected to 
another decomposition cell. 
In this we have a second 
medal as a negative plate, 
and a piece of copper as the positive plate. The second 




PRECIPITATION OF METALS. 105 

medal is connected with the. zinc of the first cell, and the 
copper with its medal. In this way, with one pound of zinc 
we obtain two pounds of copper. The application, however, 
of the second cell affords an impediment, and, therefore, the 
porous tube in the first cell should be as thin as possible. 
This very ingenious apparatus was devised by Mr. Mason, 
but has not been much used, because it has not been suffi- 
ciently known. 

(122.) The whole management of the precipitation of me- 
tals, depends for its success on a right knowledge of the prin- 
ciples of quantity and intensity, or, more correctly speaking, 
of resistance and electrical power. The latter property does 
not influence the result, as we shall hereafter see, so much as 
the former, but in most cases this should be rather abundant 
than deficient. The intensity, so far as regards electro- 
metallurgy, may be increased in two ways ; by adding to the 
series, or by using exciting liquids, capable of giving greater 
intensity, or primitive force to the galvanic current. The 
quantity of the current may be increased by enlarging the 
size of the negative plates of the battery, by increasing the 
strength of the acid solution, by using a larger anode, zincode, 
oxode, or positive pole in the decomposition cell, by di- 
minishing the distance between this and the negative plate, 
or, by that which is by far the best, by using the fluid in the 
decomposition cell in that state which most favours the con- 
vexion of the current, or, in other words, diminishes the re- 
sistance to its passage. Each of these, separately, is quite 
sufficient to regulate the quantity of electricity passing. 

(123.) To ascertain the exact quantity of electricity pass- 
ing, a galvanometer must be employed, especially for very 
feeble currents ; but, if my form of battery be used, the 
operator can judge with sufficient accuracy of the quantity 
of electricity passing, from the evolution of hydrogen from 
the negative plate. All instruments are incumbrances to the 
practical mechanic, and I believe that no workman would 



106 POSITION OF THE NEGATIVE PLATE. 

require anything farther, if my battery be used, than the 
ocular or aural test which the evolution of hydrogen affords. 

(124.) The position of the substance upon which the metal 
is precipitated, causes, in certain cases, a very singular pheno- 
menon in the deposit ; for if it be placed vertically in the 
apparatus, or especially if the upper part overhang the lower 
part of the plate, a series of lines will be produced, amount- 
ing, in some cases, to grooves of an inch in depth. The 
cause of this is easily discovered, if the solution be watched 
whilst the battery is in active operation ; it will then be 
seen that as the hydrogen reduces the metal from the fluid, 
it directly becomes colourless, and lighter than the surround- 
ing solution. It, consequently, rises and causes a current, 
which, like a stream, is reflected in various ways, at every 
elevation or obstacle. Having once made for itself a channel, 
it keeps to it, and increases till- the lines become of the depth 
which I have mentioned. This prevents the deposit being of 
uniform thickness, and makes the plate valueless. It may, how- 
ever, in a great measure, be obviated, by giving the plate a 
slight inclination, or this tendency may be entirely destroyed 
by placing it horizontally. If the metallic solution is used 
stronger, the lighter solution instantly mixes with the denser, 
and, also, when the deposition is very slow, these lines are 
not seen. 

In conducting our electro-metallurgical experiments, we 
must recollect that, in every solution of a salt, the heavier 
parts are apt to subside to the bottom, so that, in reality, at 
the bottom of the vessel, the solution is saturated, whilst at 
the top the solution contains but little metallic salt. This 
property is far more evident when the new salt is formed in 
the liquid ; thus, in every instance, where a metal is being 
dissolved, it should never be placed at the bottom of the 
solution, or else the salt will not be able to diffuse itself over 
the liquid, but will crystallize upon the metallic plate, com- 
pletely encasing it. On the contrary, if it is placed at the 



HORIZONTAL DECOMPOSITION APPARATUS. 



107 



upper part of the solution, the salt newly formed will be 
spread more evenly o^er the field, which is a circumstance 
of great importance for almost all operations. These facts 
would point out the horizontal decomposition apparatus to 
be the most philosophical, for in that vessel the metal re- 
moved by decomposition of the salt on the negative plate 
from the lower part of the solution has its place immediately 
supplied with a new portion of salt derived from the action 
on the positive pole, and thus the fluid next the negative 
plate is always maintained about the same point of satura- 
tion. Practically, however, the horizontal apparatus has some 
disadvantages which affect its universal application, for in 
this apparatus the objects to be copied cannot so readily be 
immersed in the liquid or removed from the trough. If the 
relative position of the poles be reversed, the positive being 
placed at the bottom of the vessel, crystals of metallic salt 
will encase it, and, at last, stop farther, action, whilst the 
negative pole will be surrounded with a liquid containing 
little or no metallic salt, and spongy metal will be reduced. 
I rather dwell on these phenomena, from having heard that one 
of the first practical electricians that this country can boast, 
has inadvertently recommended the positive pole to be placed 
at the bottom, clearly, however, without having tried by ex- 
periment the effect of such position. 

In conducting the series of experiments for my first edition 



which led me to recom- 
mend the horizontal appa- 
ratus for many purposes, 
I found that some metals 
could not actually be re- 
duced without it from an 
imperfect distribution of 
the salt. The use of the 
horizontal apparatus (b), 
then, by placing the posi- 



Fig. 21. 




108 HORIZONTAL DECOMPOSITION APPARATUS. 

tive pole (c), or metal to be dissolved, above the negative, 
or pole to receive the deposit (p), is onfty- to afford this equable 
distribution, and, therefore, is to be superseded whenever we 
can effect that object more readily. The solution must be 
filtered occasionally when this apparatus is employed, to 
separate any particle of dust, and the positive pole must be 
kept very clean. 

Mr. De la Rue, for the purpose of keeping up the same 
strength in his metallic solution, fixed up an extensive appa- 
ratus for ensuring that object by the circulation of fluids. He 
fixed a large tank at the upper part of the room, and another 
at the bottom. The upper one was filled with the me- 
tallic solution, and the liquid was suffered to run to the 
lower vessel, from whence it was again pumped up to the 
higher. Now this appeared to be the most direct and phi- 
losophical manner of overcoming the imperfect diffusion of 
the salt, but it caused on the negative metal such curious cir- 
cular lines, and the process of the deposition of the metal 
was so much interfered with, that the apparatus was ob- 
liged to be abandoned. This experiment is extremely 
interesting, as showing that an idea most excellent and phi- 
losophical in principle, may fail in its application, through 
the interference of some new influential circumstance, which 
it would be impossible to have foreseen. At the present 
time some electro-metallurgists agitate the solution to 
insure a proper diffusion of the metallic salt, which answers 
in many instances. 

(125.) The new deposit of metal may, sometimes, be re- 
moved with the greatest facility ; at others, it adheres with 
such firmness as to form one metallic mass, with its mould, 
from which it cannot be separated by any means whatever. 
Now we require both these properties for different purposes, 
and though, heretofore, the results have been too much the 
effect of chance, doubtless it is a matter of the utmost 
consequence to have such a control over the process, as 



\ 



ADHESION OF THE REDUCED PLATE. 109 

to obtain, with certainty, either, as we may happen to re- 
quire them. 

(126.) The adhesion of the original to the duplicate is 
termed, mechanically, buttoning down ; the non-adhesion has 
not been, as yet, vulgarly christened. Both depend on two 
facts, the enfilming of metals by air, and the possibility of 
that becoming a pole. (35.) These properties have been 
fully entered into in the first book, but here we have to notice 
their practical application. If a piece of smooth metal be 
plunged into water, it will resist wetting, and in that state 
is to be used, when we do not wish the deposit to adhere to 
its mould. In order to take advantage of this property, the 
plate is to be dipped into the solution, and the circuit im- 
mediately completed. The air would now appear to be the 
pole, and to afford a separation between the original and 
duplicate. Of course the plate should be neither heated nor 
rubbed with potash or nitric acid, previously to its sub- 
mersion ; and, above all, should not remain in an acid solu- 
tion for a single moment before the galvanic circuit is 
completed. Sometimes one or more of these circumstances 
will take place partially, and then a partial adhesion or 
buttoning will ensue. After any plate has been soldered, it 
should be allowed to remain in a cold place for at least 
twenty-four hours ; it will then regain its film of air. 

The metals are not singular in their affinity for air, nearly 
every substance in contact with it becomes coated with it. 
Paper, although having a strong affinity for water, has also 
a similar affinity for air. Thus, when large quantities have 
to be damped for printing, the air becomes a serious obstacle. 
By the machinery introduced into the Bank of England, as 
well as in' the Bank of Ireland, hj the late Mr. Oldham, 
the paper on which Bank notes are printed is placed in a 
vessel connected with an air-pump, and the air is pumped 
out, which causes a vacuum. Into this water rises, and a 
million of notes, if necessary, are in a very few minutes 



110 ADHESION OF THE REDUCED PLATE. 



wetted thoroughly. It is usual to pass the paper through 
rollers to deprive it of excess of fluid, and thus, by a simple 
application of a chemical fact, a saving of much labour is 
effected. The same principle is brought into operation in 
the process of Kyanising timber, where the air is first 
pumped from the wood, and then a solution of corrosive 
sublimate rushes into the pores of its structure as soon as 
the pressure of the air is again admitted. 

The non-adhesion of metals is not, in all cases, dependent 
on the adhesion of air ; sometimes a film of oxide, at other 
times a thin film of sulphuret, or a thin film of grease will 
prevent this property. I have at this moment before me a 
wire, the reduced metal covering which is in several distinct 
layers, caused by simply withdrawing it as many times from 
the solution, and allowing it to dry before it was again 
immersed. Eeduced copper plates will, occasionally, have 
this imperfection, being in a series of layers from a similar 
cause. 

(127.) When we are desirous to employ the opposite pro- 
perty, or to cause the new deposit to adhere, we pursue a 
contrary course ; we either heat the metal and plunge it 
into water, or rub it with a solution of caustic potash, with 
nitric acid, or else we make it the positive pole of the 
battery, and in that state place it in the solution : for then 
the surface, being quite clean, allows the deposit to take 
place on the metal itself, and not on the pole of air. It 
will then adhere so firmly, that no mechanical separation 
can be effected, as some can testify, who, ignorant of these 
facts, have entrusted valuable copper-plates in acid solutions, 
and entombed their device in a mass of copper, from which 
it could never be disinterred. 

The observations on the enfilming of the metals after 
having been exposed to the air for a short period, applies to 
many cases besides electro-metallurgy. The application of 
heat to the Daguerreotype plate, before it is exposed to the 



. 



LATERAL GROWTH OF REDUCED METAL. Ill 

vapour of iodine, is, perhaps, on the same principle, and 
doubtless any of the other modes which I have described 
for cleaning the plate will answer as well. 

(128.) The adhesion, or buttoning of one metallic plate to 
another, must not be confounded with apparent adhesions of 
the duplicate to the original, rising from the copper growing 
round the edge, and firmly embracing it. This is to be 
remedied in a great measure, in the first instance, by coating 
the edge with a layer of lac varnish or grease, which prevents 
the deposit taking place at that part. After a considerable 
lapse of time, the plate increases laterally, and covers the 
coating. 

(139.) The lateral growth of the metal of a plate is a pro- 
perty of considerable importance, for if a particle of non- 
conducting substance be placed upon a metal, it will be 
covered. This lateral growth, or the diffusion of electricity 
over a large surface, diners with every metal, nay with 
every salt of the same metal. In this way drawings made 
on copper, with varnish, may be multiplied. If a non- 
conducting substance is to be copied, by means of a thin 
film of conducting substance, a break in the continuity of 
the latter will not prevent the formation of a perfect plate. 
For the same reasons, care must be taken that no air or gas- 
bubbles adhere to the plate, for, in like manner, they will be 
enfilmed, and leave a little flaw or gap in the duplicate 
plate. To cast metals upon an air bubble, seems, at first, 
too wonderful to be believed, and, in former times, would, 
doubtless, have subjected the discoverer to destruction, on 
the supposition that he was in communication with an evil 
spirit ; but in these latter days we find it even more difficult 
to prevent than to effect. 

He who desires to make electro-metallurgy his business, 
must well consider the relative expense of the materials 
absolutely essential to his processes. An undue attention to 
this very important consideration has caused experimenters 



112 EXPENSE OF ELECTRO-METALLURGY. 

to takeout patents and incur great expense, for modes of 
working in metals by the voltaic fluid, when the object could 
be obtained in the ordinary mode of proceeding, at one half 
the trouble, one half the cost, one sixth the time, and, even 
then, nearly as well as by the galvanic current. To estimate 
the expense of working in metals by the voltaic fluid, we 
may divide the processes into several departments, — the 
single cell, the battery, the compound battery apparatus, in 
which manufactured zinc is employed ; the odds and ends' 
battery which is applicable to raw zinc; the compound 
decomposition apparatus ; Mason's apparatus ; iron single 
cell apparatus ; tin single cell apparatus, &c. 

An equivalent of power, (87.) may be obtained in the 
single cell, by the solution of 32 grains of zinc ; now as 7000 
grains of that material in a manufactured state, that is, 
rolled, are worth nearly 7c?., the equivalent of zinc in round 
numbers would cost ^ of a penny. To this must be added 
waste of zinc not used, destruction of porous tubes, and cost 
of saline excitant, which would probably bring the charge up 
to the 2V °f a penny. 

In the single battery, provided it be of my construction, 
the equivalent of power would cost about the same or rather 
less. In this case it would be the zinc (the same as in the 
single cell) plus the acid, plus the waste of zinc from local 
action, plus the difference of value between the manufactured 
zinc and the remnants that necessarily occur (52.), say, col- 
lectively, Jq of a penny. If the constant battery were 
employed, the cost would be raised from one and a half to 
twice that sum, making allowance for the value of the copper 
reduced. The application of the nitric acid batteries for 
electro-metallurgy, would entail more than treble this cost, 
raising the sum to } of a penny for the same equivalent of 
power. The expense of the power derived from a compound 
battery would be the same as that of the single battery, ^ of 



EXPENSE OF ELECTRO-METALLURGY. 113 

a penny, multiplied by the number of cells, so that if twenty 
cells were employed, the equivalent would cost (2V X 20) Id. 

By the use of spelter in the odds and ends' battery, we 
lower the price to nearly one-half, or the T \, because spelter 
is much cheaper than rolled zinc, on account of the difficulty 
of rolling, and because there is but little local action, and no 
remnant of undissolved metal to cause waste. 

The compound decomposition apparatus is the reverse of 
the compound battery apparatus, for the equivalent of 
power as obtained from a single battery, must be divided 
by the number of decomposition troughs : thus, if we have 
twenty cells, it *'ould cost (^ -f-20) ^q of a penny for each 
trough. 

Iron, to give an equivalent of power, must lose 28 grains, 
that being its equivalent; therefore, as 7000 grains in the 
manufactured state are worth from Id. to 2^., it would cost 
about -J5 of a penny, making allowance for waste and ex- 
citing fluid. 

The equivalent of power, if obtained by the agency of tin, 
of which 58 grains would be dissolved, costs, making allow- 
ance foi; waste, exciting fluid, &c, T \ of a penny, reckoning 
tin at 9d. a pound. 

From the above considerations, we form the following 
table of the bare cost of the materials to produce an equiva- 
lent of galvanic power, under different circumstances : it is 
assumed that the salt of zinc, of iron, or of tin, is of no 
value : — 

Zinc Single Cell - - -£0 °f a penny. 

Iron Single Cell - - T V — 

Tin Single Cell - - T V — 

Smee's Battery - - ^V — 

Daniell's Battery - - - t \ — 

Grove's Battery - - 7 . — 

Odds & Ends Battery T \ — 

Compound Battery - g^ x by the number of cells. 



Compound Trough - ^\ 4- by the number of troughs 

7 



114 EXPENSE OF ELECTRO-METALLURGY. 

Having obtained this table, an important clue to the 
expense is arrived at ; for, if we are desirous of ascertaining 
the cost of the reduction of a metal from its particular salt, 
we ascertain its equivalent number (87.), then the value of 
that quantity, and lastly, by adding this cost to that of the 
power, we arrive at the bare value of materials for that 
equivalent. Having ascertained the value of the number of 
grains corresponding to the equivalent number of a single 
proportion, we learn the cost of 7000 grains, or one pound 
avoirdupois. 

Let us suppose, for instance, that we are anxious to know 
the cost of the reduction of copper from its sulphate, we find 
that the equivalent of this salt is 125, which, at 4d. for 
7000 grains, or one pound, would amount to 7000 : 4 : : 125 : 
y 1 ^ of a penny. This we add to the number appended to the 
particular process against the above table, which would make 
the cost for one equivalent of copper, or 32 grains, as reduced 
by the single cell, nearly } of a penny ( t \ + ^q = } of a 
penny). Then, to ascertain the cost per pound, as 32 the 
equivalent of copper : } of a penny : : 7000= to about 
2s. Zd. a pound. On the negative side, we have, in addition, 
a certain waste of materials ; there is more metal reduced 
upon the edges than we require, and some copper left in the 
exhausted solution, of which it is impossible to give exact 
estimates. 

So much for the cost of the materials in a single cell, and 
to put them in the form of an equation, C, the cost = (e) 
value of an equivalent of power +(s) the cost of an equiva- 
lent of metallic salt — 

C=e+s. 
To ascertain the cost of our materials in a battery appa- 
ratus, the equation would be altered, C, the cost = e, value 
of equivalent of power +m, the price of an equivalent of 
rolled metals suitable for our positive pole. To this we must 



EXPENSE OF ELECTRO-METALLURGY. 115 

add a loss for the impurities in the metal, the loss from rem- 
nants, and the occasional cost of a renewal of the metallic 
solution. 

Cr=e+m. 

Let us take an example of the precipitation of copper from 
the single battery apparatus. C=e ^d. + m, with a little 
loss T \ = about *, for thirty-two grains of metal reduced. In 
this case, rolled copper is estimated to be worth one shilling 
per pound. 

Although every person ought to make the calculation for 
himself, before he enters into any large operation, I subjoin, 
as a rough guide for the electro-metallurgist, another table, 
showing the price of the reduction of copper from its sulphate 
by each of the methods detailed above : — - 

P 
Single cell zinc 

iron 

tin, nearly 
Single battery 
Daniell's 
Grove's 

Odds and Ends' - 
Ten cell compound battery 
Ten cell compound trough 

Mason's plan j^Vcdl 

Besides the elementary cost, we have to pay for the 
negative metal, or moulds on which our metal is reduced, 
we have the time requisite to keep the apparatus in action, 
we have the rent of the room in which the operations are 
conducted, and a hundred other circumstances, for which no 
general computation could possibly be given, as they vary 
with every case. All these things will be considered in the 
description of the processes. The preceding equations show 
clearly that electro-metallurgy shines conspicuously forth for 
utility, where the value of the metal is great, and its equiva- 



quivalent. 


s. d. 




2 3 per lb 




- 1 6 

- 3 


id. 


2 3 


$d. 


3 


Id. 


3 7 


±d. 


- 1 

- 10 5 


M 


- 1 5 


t* 


2 3 


A* 


- 1 3 



n 



116 BXPENSE OF ELECTRO-METALLURGY. 

lent high : thus, by applying our equations to gold, we find 
that the equivalent of power is nothing compared with the 
value of the metal, for we reduce two hundred grains of 
gold for ¥ \ of a penny, whilst the metal is worth nearly 21. 
For this same cost of ■£-$ of a penny, we can obtain only 
thirty-two grains of copper, that being its equivalent ; but 
if we desire to make hydrogen, we can only get one grain 
for our money. This simple principle prevents the em- 
ployment of the galvanic power for the production of gas 
for illuminating purposes, as, if we make our calculations, 
we shall find that the cost of materials for this purpose 
would be about 11. 10s, per 1000 cubic feet, whilst the gas 
companies supply us at four shillings with the same quantity. 
Had the equivalent of hydrogen been 200, the cost of 
its production would have been only nine-pence, which 
would have been the means of converting every coal-gas 
company in the country into a galvanic gas company, and 
with the gas, such an abundant supply of galvanic power 
would have been available for electro-metallurgy, that all 
other modes of working many metals would have been en- 
tirely superseded. 

We know for certainty that zinc and other metals are not 
employed for the voltaic currents which exist in animal 
bodies, and we have reason to infer that hydrogen and 
carbon are the materials used by nature. The equivalents 
of these elements only being 1 and 6 respectively, it is proved 
that for economy they should alone be employed for the 
positive pole of the battery. For hours I have sought to obtain 
a working battery from ordinary hydrocarbons, but hitherto 
have totally failed. The value of the steam engine over 
electrical contrivances, depends upon the cheapness of coals 
as compared with zinc ; for if ever the philosopher should 
discover an effective carbon battery, then will the steam 
engine cease, then will gas companies be compelled to stop 
their works, and a total revolution will be produced in all 
the physical forces employed by man. 



117 



CHAP. II. 

ON SUBSTANCES CAPABLE OF RECEIVING THE METALLIC 

• DEPOSIT. 

Substances on which the deposit may take place, 130 — 131. Metals, 132 
— 136. Non-conducting substances; Sealing Wax, White Wax, 136 
— 139* Absorbent substances, as Paper and Plaster of Paris; means 
of rendering them non-absorbent, 139 — 141. Gutta percha, 141. 
Means of copying non-conducting substances by metals; by Plumbago, 
143—145. Comparison between the methods, 145. 

(130.) The voltaic deposit of metal may take place upon 
any conducting substance, which is capable of acting the 
part of the negative metal, in the arrangement. The laws 
which relate to this, are the same which regulate, in a similar 
manner, the plates of the battery. The deposit may be 
effected upon most metals, except the earthy and alkaline, 
and upon any alloy or compound of them. It may, likewise, 
take place upon charcoal and plumbago. When the metals 
are employed, the effect is evident enough, for the arrange- 
ment differs in nothing from that of a Daniell's battery. 

(131.) Where we desire the duplicate to possess a surface 
and form exactly like those of the original, it is of the utmost 
importance that the metal on which the deposit is to take 
place, should not of itself decompose the fluid, because, in 
that case, the duplicate is sure to be more or less impaired. 
To illustrate this, zinc, lead, tin, or iron, in sulphate of 
copper, precipitate the copper immediately from its solution, 
but the former metals are dissolved exactly in equivalent 
proportion with the reduction of the latter. The solution of 
this metal impairs the surface, and renders the duplicate less 



118 



LIST OF SUBSTANCES FOR MOULDS. 



perfect. This may be prevented, in a great measure, by 
taking care that the voltaic current is passing at the moment 
when the metal is plunged into the fluid ; and this mode of 
proceeding is supposed, by many, entirely to supersede the 
electric affinity, as it is termed, or the spontaneous action of 
the metal on the fluid. But I can decidedly affirm, that no 
battery, even of large series, will entirely prevent the solu- 
tion of the more oxidizable, and the reduction of the less 
oxidizable metals, because it is impossible to protect by a 
negative tendency a metal where the hydrogen is in a con- 
dition to be absorbed. 

The metals which can be employed with advantage to 
receive a deposit of any other metal, are, therefore, those 
which are not acted upon by the particular fluid in which 
they are immersed ; those, however, which are but slightly 
acted upon, may still, in some cases, be employed. The 
same thing may be said of the non-metallic bodies when 
coated with a thin film of conducting substance, for it is 
essential, in order to make an accurate cast of any body, that 
it should not be decomposed by the fluid in which it is in- 
serted, but remain entire during the time requisite for its 
immersion. The following is a short list of substances which 
may be used to receive the deposit of metal : 



Carbon - - - In all metallic solutions, acid, neutral, or alkaline. 

Platinum - - Ditto ditto ditto 

Gold - - - Ditto ditto 

Palladium - - Ditto ditto 

Silver - - - In all alkaline, in all but the preceding, saline and 

acid. 

Copper - - - Ditto 

Lead - - - Ditto ditto 

Bismuth - - Ditto ditto 

Antimony - - Ditto ditto 

Tin ... Ditto ditto 

Iron - - - Ditto ditto 

Zinc - - In some alkaline ditto 



LIST OF SUBSTANCES FOR MOULDS. 119 



NON-METALLIC SUBSTANCES. 



Gutta percha - 


In all saline 


or acid solutions. 




Sealing wax - 


Ditto, not in alkaline, 




White wax 


Ditto 




ditto 


Bees' wax and rosin 


Ditto 




ditto 


Stearine 


Ditto 




ditto 


Spermaceti - 


Ditto 




ditto 


Plaster of Paris pre- 








pared 


Ditto 




ditto 


Some animal sub- 








stances 


Ditto 




ditto 


Most vegetable sub- 








stances 


Ditto 




ditto 



Now by the preceding table we perceive that some sub- 
stances may be immersed in one solution with impunity, 
while others would be destroyed by its action on them. It 
is, therefore, important to know, when we have a substance 
which is acted upon by any metallic solution, how to make 
a reverse from it that shall not be injured. For convenience 
a table is appended, showing at one view the modes of pre- 
paring moulds of different substances. The perpendicular 
row is a list of the objects to be copied, the horizontal the 
means of multiplying them. Suppose the operator had a 
valuable silver medal, of which he was desirous of making 
a fac-simile, he would look in the table against silver, and 
would there find that he could make a mould, or reverse, in 
copper, by electro-metallurgy ; but to this he would doubt- 
less object. He would then see by what other methods he 
could also make a mould, and he would find that he would 
prefer plaster of Paris, as least likely to be injurious to 
his medal. Having made the mould in plaster, he suc- 
ceeds with each of the processes given, and perhaps he 
would see from the former table, that, when prepared, it 
might be placed in any saline or acid solution of copper, to 
form the fac-simile. 



/ 






















120 


























w 


5 

Bh 

o 

w 

H 
to 

PL! 


if 

1 

1 

>> 


6 

4-1 

^3 


6 
3 


d 


d 
33 


d 

4J 

4-J 

^3 


d 

4-0 


d 
n3 


d 

^3 


d 

^3 


d 
?3 


d 
^3 


d 

4-i 

^3 


d 

4J 

^3 


d 

4-1 
4-J 

^3 


d 

^3 


d 

4g 

^3 


d 

4-1 

4-1 

^3 


6 

4J 

»3 


d 
^3 


| 


6 
^3 


d 

4-» 

4-3 

'<B 


o 

B 

o 




1 

CQ 

co 

P. 

X 


d 
'B 


d 
^3 


d 
B 


d 
B 


d 


d 

4J 
^3 


d 
3 


d 

^3 


d 
^3 


i 
• 


i 


I 


a 
o 
"53 
Jj 

>> 

X 


© 

1 

QQ 
© 
k 

Pi 

X 


d 

^3 


• 


©* 

k 

| 

CD 

£ 

pi 
>> 
x> 


d 

4-i 

?3 


i 
■ 


■ 


2 

i 

00 

Pi 

S>3 

X 


6 

t-3 

?3 


►— 1 

s 
3 

N 

O 

1 

1 


* 2 

10 ^ 


1 

X 


6 
'B 


6 

4-1 

^3 


| 
^3 


d 

4J 

8 


d 

4-> 


d 

4-1 
5 


d 
^3 


d 

4-> 


d 
«3 


■ 




1 
1 


o 
'S3 


1 
I 


p 

.2 
"S3 

s 


d 
1 


d 

4-3 

4-> 

^3 


d 

4-3 
4-> 

^3 


■ 
• 


i 


p 
.2 

"53 

a 

Xi 


S 

4-> 

^3 


« 
o 

1 

o 

s 

I— t 

M 


z. 

M 

H 

10 


§ 
co 


| 

B 


d 

4-3 

^3 


d 

4-1 

^3 


d 


d 

4-1 

^3 


d 
B 


d 
1 


1 


■ 


• 




• 
1 


1 

1 


1 

53 

X 


■ 
i 


■ 


p 
.2 

"Ed 

X 

I 

CO 


d 

4» 
4-3 

T3 


i 


• 

i 


1 

So 


2 
?3 


fa 

O . 

O H 

-< 


© 

X 
X 


6 

B 


d 
•p 


d 

B 


d 

'3 


© 

-© 

X! 

13 
>> 

X 


• 
• 


© 

-© 

X 
© 

% 

>> 

X 


. 


■ 
i 


> 
• 


■ 
■ 


' 


© 

-© 

XI 

© 

X 


• 


©' 
-© 
X 
© 

>> 

X! 


d 

4-J 

^3 


© 

-© 

X 

o 

•x 

© 

X 

© 

2 

o 

CO 


d 
^3 


■ 


• 


© 
-© 
X 
o 

•x 

© 

>> 

X 


d 

4-» 

^3 


3 

CO 

§ 


P. 

W 


.2 
1 

'S3 

00 

S 
© 

k 

© 

P. 


o 
^3 


| 


d 
^3 


' 


' 


■ 


fab 

.2 

o 
k 

a 
.2 

'So 

CD 
P 
g 

X 


• 


| 

55 

6 

© 
P, 

X 


i 


• 


1 


1 

1 


I 


• 


• 


i 


• 


■ 


i 


• 


• 


1 

5 

i 

a, 

B 

8 
1 


pi 

M 

a* 

a. 
o 
o 


& 

15 
© 
2 
6 

© 

© 
© 

X 


6 

4-1 

^3 


o 
?3 


d 

B 


d 

4-> 
^3 


d 
^3 


d 
^3 


1 

03 
CO 

3 

o 

© 
Pi 
>» 

X 

§ 

^3 


© 

2 
6 

b 

© 
^© 

"© 
^3 


d 
^3 


d 

4-> 

^3 


d 
^3 


o 
^3 


. 


• 


k 

| 

© 

2 
6 

k 

© 
© 


o 
p 


k 
P 

© 

2 

6 
k 

o 
^© 

X 


d 
^3 


• 


- 


la 
© 

k 
© 
© 
© 
>> 
X 


d 
•B 


to 
•J 

a 

s 


k 
© 
Pi 
Pi 

o 


k 
© 
> 


2 


2 
J 

3-1 


T3 
© 


o 

00 

5 


p 


a 

o 
u 


© 

k 
© 

X 

O 


M 

bX) 
•2 

i| 

© 


co 

B 

Pi 

s 

5 
^d 
3 
M 

p: 

*0Q 
© 
© 


© 

1 

S3 
© 
02 


© 
o 

g 

© 
P. 
172 


u 
P 

X 

Pi 
'3 


2 

k 

© 

Ph 

4^ 
P 

5 


00 

i 

k 

© 


ho 
P 

1 

X 

9 

© 

a 

3 


© 

I 

CQ 

X 

p 

02 

p 
'2 


© 

I 

OS 

X 

P 
W 

© 

a 
© 
© 


2 

p 


CO 
00 

ci 

.2 

'CO 


CO 

CD 

3 

CO 

e3 
oT 
© 
^3 
O 

M 
co 

p 
o 
© 
© 
•x 

»2 


o 

^3 

co 

P 

1 
5 



PLATINUM, GOLD. 121 

(132.) Carbon, from its cheapness, from its indestructible 
nature, and from its being unaltered in all metallic solutions, 
is invaluable for electro-metallurgy. One variety of it, 
graphite, or plumbago, usually called black-lead, has a most 
extensive application, which we shall hereafter have occasion 
more especially to describe. 

Platinum, from its being unaltered by any solution, holds 
an important place for the reception of every metal ; its 
great price, however, must always be an impediment to its 
general use. 

(133.) Gold is equally valuable with platinum, but is still 
more expensive ; yet when extended to that state in which 
it exists as gold-leaf, it may be applied over the surface of 
any soft substance, and thus a metallic surface is presented. 
This plan may be employed with other metals, such as silver 
or tin ; but we have other methods which render all these 
modes unnecessary. 

(134.) Silver only reduces gold, platinum, palladium, and 
two or three more metals from these acid solutions, and 
therefore may be employed as a negative one for the reduc- 
tion of metals. Silver-leaf, of a thickness of about one square 
foot to the ounce, and made of pure metal, is much used by 
foreign forgers. The process they adopt is, to place the coin 
to be copied on a piece of wood, and upon the coin they place 
a piece of this thin silver. They beat it gently with a 
wooden mallet, till a perfect impression is taken on the 
metal, a result soon obtained. They then copy the opposite 
side of the coin in the same way. The two impressions are 
then soldered together, and the manufacturer sallies forth 
and risks his neck for the illicit shilling which has cost him 
this labor. The reader will doubtless have no inclination 
to practise this fraud, and, therefore, it is unnecessary to 
enter farther into the process ; but it should be borne in 
mind, that the same means may be employed with a better 

intention by the electro-metallurgist, to obtain a mould. 

7* 



122 ALLOYS OF LEAD, TIN, ETC. 

Copper may be used for the reception of many metals, but 
unless the object to be coppered happens to be a mould, we 
cannot easily make a reverse in this metal, except by electro- 
metallurgy. 

(135.) We have now to treat of the alloys of lead, tin, 
bismuth, antimony, and zinc, which demand especial atten- 
tion, because there are means of casting these alloys, and of 
making reverses, moulds, and medals, by more ready methods 
than we possess for any other metals. It has been remarked 
that these alloys have melting properties, not only below the 
mean of the melting points of the respective metals which 
compose them, but even some of them considerably below the 
fusing point of the most fusible metal that enters into their 
composition. To some of these alloys we owe the manufac- 
ture of type, to others the process of stereotyping, to others 
that of poly typing or clichee. The composition of the type- 
metal is stated to be 1 part of lead to 16 of antimony, and 
sometimes a portion of copper is added ; this proportion 
probably varies at each foundry, as they generally consider 
that part of the business a secret. Other compositions are 
given as 6 to 2, 4 to 5, or 4 to 1 of antimony to lead. In 
the foundry there are a number of crucibles, each heated by 
a charcoal fire, one being allowed to each workman. To 
make a type, the operator takes a little of the melted alloy 
in a small ladle each time, and pours it into the mould which 
has the counterpart of the letter he wishes to take. The 
moment it is in the mould, he carries it suddenly upwards 
with a jerk above his head, by which means the metal is 
forced into all the fine parts of the work and a good 
impression is insured. Now we might expect that those 
who clay by day work at this occupation, would attain to 
certainty in their proceedings ; but this is by no means 
found to be the case, for they form a very large number of 
imperfect types which are obliged to be re-melted. I give 
this process to show that with those about to be detailed a 



ALLOYS OF LEAD, TIN, ETC. 123 

strong analogy to coining is presented. In the first case, it 
is with a fluid, or semi-fluid, metal ; in the last with a solid 
mass. The alloys which may be used for these purposes are 
very various, according to the object from which we desire 
to obtain a reverse, for as a great latitude is allowed f in the 
fusing point, so at one time we prefer the more fusible, at 
another that which melts at a higher temperature. 

The following is a list of alloys which are employed by 
various authors, to which should be added all the composi- 
tions of type-metal, last described, and as antimony possesses 
the property of expanding in the act of cooling its alloys are 
well adapted for casting. 

Tin. Lead. Bismuth. Zinc. 
14 10 

2 5 10 1 



3 





1 


1 







4 


1 


1 










5 


3 


5 


8 





fuses about 212° Faht. 


6 


1 


1 


2 





said to fuse at Faht. 200. 


7 


1 


2 


3 





ditto 200. 


8 


1 





1 


1 


ditto 200. 



The alloy No. 5 is called the fusible metal of Sir Isaac 
Newton. No. 6 is the fusible alloy of Rose. The two last 
are after the French. Sometimes a little mercury is added 
by the instrument-makers to render the alloy more fusible, 
but this ought always to be discarded in electro-metallurgy. 

All these compounds are used at a point between the 
fluid and the solid state, for at that heat they assume a pasty 
appearance, which is probably caused by the alloy consisting 
of two parts, one more fusible than the other. In fact, if 
we examine the mass very attentively, it appears to be com- 
posed of a quantity of perfectly solid metal in a fine state of 
division suspended in another portion of alloy perfectly fluid. 
Having obtained our alloy in this state, it is ready for the 



124 CLICHEE. 

process of making our reverse, and this process is termed 
the clichee. The alloys marked 1, 2, 3, 4, as well as the 
compositions for type-metal, will answer for iron, brass, 
copper, or other hard substances ; perhaps No. 2 and No. 3 
will be found, after type-metal, entitled to the preference. 
When we desire the clichee from wood, sulphur, or from 
another clichee, w T e must employ those alloys which fuse 
most readily, and Nos. 5, 6, 7, and 8 come into use. If 
hard metals are used from which to clichee, we should take 
care to clean them thoroughly before using, and always 
employ them in a cool state. In using one clichee for 
making a second, we must take care to employ a less fusible 
alloy for the first than for the second ; thus the type-metal 
and Nos. 1, 2, 3, 4, answer as a primary mould to make 
casts in 5, 6, 7, 8. To clichee from Plaster of Paris, the 
material must be prepared either by linseed oil, gum, or 
gelatine, which processes will be described when treating of 
those substances, and sulphur moulds must be employed 
within a few hours of their manufacture. 

The simplest mode of making a clichee is to pour a little 
of the fused alloy on any flat surface, then to skim it clear 
with the edge of a card that the surface may be most 
perfectly bright, after which we should wait till it is nearly 
at the point of cooling, when with a considerable jerk the 
matrix is to be brought down upon the alloy, by which 
operation the fluid part will be forced out in all directions, 
and a reverse equal in polish, sharpness, and beauty to the 
original, will be instantly obtained. If the alloy is used too 
hot, the surface is apt to present a crystalline appearance ; 
it is, therefore, very important that the object should be cool 
enough to make the alloy perfectly hard, as soon as the blow 
has driven the metal into all the finest lines. When taking 
a clichee from an intaglio the air has not always time to get 
away, in which case little holes or bubbles are very apt to 
be caused. The surplus metal round the edges of the mould 



CLICHEE. 125 

so formed, is then trimmed off in a lathe, but this operation 
is generally unnecessary for electro-metallurgy. 

The Italians have a method of taking very perfect moulds 
with these alloys. They take a portion of the melted mass, 
and place it on a piece of paper ; upon this they lay the 
medal, and under both a piece of carpet ; upon the medal 
they place a log of wood, and then a sharp blow on the wood 
will ensure the sharpness of the cast. The worth of a cast 
thus made, is from sixpence to half-a-crown. I have before 
mentioned, the clichee is nothing but a process of coining, 
and sometimes a sort of coming press is used for these 
purposes ; the medal or other object is fixed either by mastic 
or by screws on a piece of metal, which descends with force 
on the semifluid alloy. Previously to the operation of 
striking, the object is suspended by a cord passing through a 
ring, and attached to the rod of iron connected with the 
piece of metal. When every thing is ready, the doors are 
shut and the cord let loose, which allows the object to fall 
with great force on the metal. 

An impression may be given to a perfectly clean bright 
surface of sheet lead, by placing upon it the object to be 
copied, and then with a steady hand dealing a heavy blow. 
By this mode even a sealing-wax impression may be copied, 
although this, at first sight, would appear hardly credible. 
By pressure alone, it would be difficult to obtain the result 
which can be given by the blow. Rolled lead, first scraped, 
in order to remove any oxide from the surface, and then 
flattened by running it through a press upon a polished iron 
plate, will readily take the impression of the most delicate 
work or engraving. The object to be copied is simply to be 
placed upon the lead, and then the two are to be sent once, 
and once only, through the printing-press, as in the ordinary 
operation for taking a print. The pressure in rolling is far 
greater than can be given by direct pressure, though there 
are instruments used by embossers capable of exerting great 



126 SEALING-WAX. 

power. The disadvantage of forming moulds by rolling is a 
liability of distortion of the image from imperfect stretching 
of the metal. 

The stereotype is not of much value for electro -metallurgy ; 
moulds made of stereotype metal may, however, be employed 
should there appear to be any occasion to use them. Stereo- 
type-casts are only made practically from plaster of Paris 
reverses : thus to stereotype this page a plaster-cast would 
be taken of the type when set up, and this would then be 
thoroughly baked in an oven to expel all moisture. The 
plaster mould is next placed face downwards in a box, and 
confined in that situation by a plate of iron, when the whole 
apparatus is lowered into a caldron of melted alloy kept over 
a fire. It is suffered to remain in that situation a few mo- 
ments, when it is withdrawn, and the vacuity caused by the 
contraction of the metal during the process of cooling is 
supplied by the workman. All the metal moulds will doubt- 
less soon be discarded from electro-metallurgy for gutta 
percha. 

(136.) Non-conducting substances are of three kinds : — 
substances having no affinity either for the metal or the 
solution ; substances acted upon by the solution ; and, lastly, 
substances capable of combining with the metal thrown 
down. Those of the first class are by far the most valuable, 
but are not very numerous. The best of these is sealing- 
wax — a composition of shell-lac, Venice turpentine, and 
colouring matter. Dr. Ure gives, as the proportion in 
which these are used, four, one, and three. The manu- 
facturers have several varieties, the most expensive of which 
is the best for making seals. Some of them are extremely 
hard, as for example, a black wax which is used for filling 
up the letters in the engraved plates of shop- windows, but I 
do not know how a difference of composition can affect the 
properties of the wax in this important manner. The use 
of sealing-wax is attended with considerable expense, as 



SEALING-WAX. 127 

good wax cannot be purchased under three and sixpence or 
four shillings a pound, but it takes impressions of objects of 
the greatest delicacy with the utmost accuracy. Every one 
uses this substance, and sealing is one of those operations in 
which every one thinks that he excels his neighbour in the 
manner in which he performs it ; but, however well satisfied 
he may be with his skill in the small way, yet the manage- 
ment of large seals is attended with great difficulty and 
uncertainty. Proof-seals are made by engravers, by holding 
a piece of card over a flame, and rubbing, gradually, a stick 
of wax, previously softened by heat, upon the heated card, 
till a sufficiency is obtained, when the coin is to be pressed 
upon it. Very large seals are made by taking a good-sized 
stick of wax, and holding it in a flame, not only till the 
point, but even three or four inches of its length are lighted. 
It is then to be held over a piece of paper or card, when 
large drops of melted wax will keep falling, and in a short 
period a considerable quantity will be melted. The flame of 
the stick is to be blown out, and the fluid mass well stirred 
round and round, till all the air- bubbles are dispersed, and 
a clear surface of semi-fluid wax is exposed. It is now 
ready to receive the impression of the object of which we 
are desirous of obtaining a copy. This is to be laid upon 
the wax, and pressed with considerable force, and lastly, 
plunged into cold water, so as to cool it suddenly. Much 
less difficulty attends the use of a metallic die, for that 
abstracts the heat, and does not adhere. The accuracy with 
which sealing-wax takes impressions with care, is shown by 
its copying the lines on mother-of-pearl, and analogous sub- 
stances, which naturally possess the property of decomposing 
the rays of light, and the same colours which exist in the 
original are also to be observed in the copy. 

When we are desirous to obtain an impression in wax 
from wood or similar substances, they should be previously 



128 WHITE WAX. 

brushed over with a little salad oil. In these cases, by 
plunging the wax into cold water, its surface is apt to sink 
in places, and thus becomes uneven. Very large seals 
have been made of sealing-wax, by means of placing the 
mould on the semi-fluid composition, and subjecting it to 
hydrostatic pressure. In this way operators have suc- 
ceeded in making perfect casts of six or more inches in 
diameter. 

(137.) White wax may be used for taking casts, and can 
be procured with least expense by buying the waste ends of 
wax candles, which may be readily melted over a lamp. 
The object to be copied is to be very lightly oiled with a 
hog's-bristle brush previously dipped in that fluid. A 
moment's exposure of the medal to a current of steam, or 
even to the breath, will answer the same purpose, because 
a film of water, for which wax has no affinity, covers the 
medal, and, therefore, causes a separation between the wax 
and the metal. A narrow strip of paper should then be pro- 
cured which is to be wound round the object to be copied 
and kept in its position by a piece of twine Fig. 28. 

tied around it. The ends of the paper may 
be even still better kept together by a 
little bit of melted sealing-wax. If the 
object to be moulded happens to be a 
medal, this is easily accomplished, and in 
other cases the same thing may be, with but 
little more difficulty, effected. By this 
proceeding we form a kind of rim to the medal. The fluid 
wax is then to be poured into the cup thus formed, care 
being taken that no bubbles of air adhere to the medal. The 
heat at which the melted wax is used influences the success 
of our operation. If the object to be copied be small, it need 
not be so warm as if it were of considerable size. The con- 
ducting power of the body requires a similar regulation of 
temperature, for if it be a good conductor, a metal for 




WHITE WAX. 129 

instance, it has the power of abstracting the heat from the 
melted wax so rapidly that a higher temperature must 
be employed. As a general rule, the surface of the object 
should be entirely covered with fluid wax a second or 
two before hardening commences at any one point, and in 
the same way the wax should not be so warm as to remain 
long before it begins to set firm, it is then suffered to re- 
main not only until it becomes solid, but even quite cold, 
which will not take place in less time than two or three 
hours, on account of the wax being a bad conductor of heat. 
It may then be taken off by gently pulling the wax-cast from 
the medal. 

Plaster-casts may be even copied in wax, by simply oiling 
the plaster with a little sweet oil, previously to pouring in 
the fluid, and thus a perfectly sharp reverse of the plaster 
will be obtained. A still better method of taking a reverse 
from plaster, is to let it absorb as much hot water as it will 
take up without any remaining on the surface. For this 
purpose the cast is placed in water not above half its height, 
and as the water penetrates by capillary action, the surface 
begins to assume round the edge a slightly dark colour, and 
the eye can accurately trace its progress till the action is 
finished. It is then to be enclosed in paper, and melted wax 
poured upon it while it is warm ; after which the whole is to 
be allowed to cool, when the wax will separate from the 
plaster with the greatest facility. In this process much of 
the success of our labour depends on the quantity of water 
employed, a very nice adaptation of that being requisite. If 
there is too much water it will then be drawn up between 
the wax and the plaster, after the former has been poured 
upon the cast, and a wavy hollow surface will be given to the 
mould which completely unfits it for electro-metallurgy. If 
too little water be used, the wax will penetrate into the pores 
of the plaster of Paris and adhere to it. The plaster must 
not be soaked in water one minute longer than necessary, for 



130 SPERMACETI. 

that will soften the structure, and render the surface infinitely 
more liable to tear up and be destroyed upon the separation 
of the wax reverse. Should the slightest adhesion exist, it 
shows that the plaster has not absorbed sufficient water, a 
circumstance which the operator must avoid another time ; 
if, however, a very slight adhesion should exist, it may, 
generally, be overcome by soaking the mould and cast for a 
few minutes in water, when frequently a spontaneous sepa- 
ration will ensue. Those engaged in making moulds do not 
esteem wax as the best substance for taking casts, and, 
perhaps, with justice, from the reverses made by this sub- 
stance not entirely possessing the sharpness of the original, 
the edges of the sharp parts frequently being rounded and 
dull. 

The substance called stearine makes, also, excellent moulds, 
for which purpose, I believe, it has been much used by 
Jacobi. Stearine is made from common tallow, by pressing 
it with an hydraulic machine and squeezing out the fluid 
parts. This process is however imperfect, a portion of the 
oily matter being always left. The metallic- wick candles 
are said to be an example of this mode of proceeding. A 
far better operation of preparing this substance is to saponify 
the tallow by potash, soda, or, what is more used, lime, and 
then decompose the salt thus formed with dilute sulphuric 
acid. In this way excellent stearine candles are made, 
which in illuminating powers and cleanliness are inferior to 
none. The observations applied to wax are suitable also to 
stearine, the proceeding in both cases being alike. The 
price of raw stearine in London, at the present time, is about 
one shilling a pound. Spermaceti is perfectly analogous to 
stearine in its properties. It is the solid part of the oil 
of certain whales, particularly of the physeter macrocephalus, 
or sperm whale ; the best is to be obtained from the head of 
the animal. It is to be used in the same manner as wax and 
stearine. 



PAPER. 131 

(138.) A mixture of equal parts of bees'-wax and rosin 
may be employed for taking easts, and may be used in a 
similar manner to wax ; sometimes they add a little turpen- 
tine, and increase the quantity of rosin. This composition 
is used a great deal by the Italians, but care must be taken 
not to use the fused mixture too hot. The composition 
should be melted, and then allowed to remain till the bubbles 
have dispersed, and till it becomes nearly as thick as treacle, 
when it is to be poflred over the object, in the same way as 
wax. 

(189.) Of the second kind of non-conducting substances, 
there are several varieties ; paper, plaster of Paris, &c., 
which are acted upon by the fluid. Paper is of no great 
value for obtaining a reverse from any object ; by the em- 
bossing machines, however, we can obtain from metals and 
hard substances, a cast like the ordinary stamps, and we can 
effect the same result by placing two pieces of paper over 
the object and rubbing the upper one with a black-lead 
pencil, by which means the paper is forced into every de- 
pression. Paper rapidly absorbs the fluid of the solution, 
and becomes rough, and therefore, must be treated with 
various substances, in order to give it a perfectly uniform 
surface. It may be brushed over with a little drying oil, 
such as linseed or nut oil, to the former of which I give the 
preference. The oil should be thoroughly boiled, that it 
may dry as quickly as possible, after its application to the 
paper. The substance to w T hich the oil is to be applied, 
should be clean. It is then to be brushed lightly over with 
a camel's hair brush till all absorption ceases, and the surface 
is left shining, owing to the small quantity of oil still re- 
maining upon it. Great care must be taken that the plaster, 
or paper, be just saturated, and no more, as the superfluous 
oil, by drying on the surface, will fill up the space between 
the fine lines. The paper must then be left to dry for about 
twenty-four hours, and, if possible, exposed to sunshine, as 



132 VARNISHES. 



the rays of light favour the absorption of oxygen, a circum- 
stance absolutely essential to the drying of linseed oil. It is 
then ready to receive some conducting substance, of which 
I shall hereafter speak. This mode of treating paper 
appears, for most purposes, to be superior to every other. 

Varnishes may be applied for the same . purpose, and as 
some of them dry more quickly than the oils, their use is 
attended in some cases with advantage. The principal of 
these is the white hard, copal, mastic, and carriage varnish. 
The first dries in a few minutes, and should be applied until 
a small quantity bears out from the surface. It is best 
adapted for highly-glazed papers, where the quantity of size 
prevents the absorption of the more viscid varnishes. The 
mastic fulfils its purpose very well, but no particular ad- 
vantages attend its application. The carriage varnish may 
be sometimes used, but great care must be taken that it does 
not clog up the fine lines, otherwise it is a most valuable 
varnish for this purpose, and leaves a very smooth surface. 
It would be in vain to describe all the modes which may be 
adopted to render paper non-absorbent and smooth, — it is 
the principle to which I wish to direct particular attention. 
Sometimes a mixture of bees'-wax and rosin previously 
fused, may be applied, particularly to the absorbent papers. 
The paper should be held over a flame so that it does not 
burn, and the composition rubbed upon the opposite side to 
that on which we desire to make the copy, till the paper is 
thoroughly infiltrated, when it will be found not to pass 
beyond the surface. The paper is hard in a few minutes, 
and ready for the solution. This is an excellent process and 
one which may be frequently adopted. Sometimes rosin 
itself may be used, but it is apt to be brittle. Other sub- 
stances may be employed in a similar maimer, as balsam of 
Canada, &c. 

(140.) The preparation of plaster of Paris is of the utmost 
importance, and the destruction of its absorbent property is 






PLASTER OF PARIS. 133 

to be effected by means similar to those employed in the pre- 
paration of paper. Plaster of Paris is sulphate of lime, or 
gypsum, deprived of its water of crystallization by heat. In 
this state it has such an affinity for water, and is capable of 
taking up so much, that when the powder is mixed with 
water till it becomes of the consistence of cream, it sets after a 
few seconds into a hard mass. In the manufacture of 
plaster-casts, we must pay attention to several little niceties, 
in order to get rid of all the air-bubbles. These arise from 
two causes, either from the adhesion of the air to the plaster, 
or from the plaster carrying down air with it, when added to 
the water. The first is to be remedied by using fresh burnt 
plaster, which is always adopted by the cunning stereo- 
typers, for they state, that if it simply stands a fortnight, the 
casts will not be so good. The workmen cannot explain 
this, but the rationale was well known to Mr. Wyatt, our 
celebrated sculptor, who told me he attributed it to the 
adhesion of the air ; and that thus many delicate casts were 
injured. He places the dry plaster in a saucepan over the 
fire, and heats it, when it heaves from the discharge of the 
gas, and is then ready for use. When we desire to make a 
plaster cast, a sufficient quantity of plaster should be placed 
in a basin, and water poured upon it till it is completely 
covered. The bubbles having ceased to rise, the plaster and 
water are to be thoroughly mixed by rubbing them together. 
Mr. Williams, in an interesting lecture delivered before the 
Royal Institution, recommended that a basin of water should 
be taken, and the plaster gently shaken into it, and allowed 
to stand for half a minute, when the superfluous water was 
to be poured off, and the semi-fluid mass remaining being 
stirred up, is then in a state ready for use. Now these two 
processes are somewhat the reverse of each other, but both 
agree in principle : that is, by both methods the operator 
endeavours to get rid of adherent air as much as possible. 
Some excellent mechanics declare that the first method is 



# 



134 PREPARATION OF PLASTER MOULDS. 

the best, others that the last is the only one that can be 
adopted with success, but as both sets of workmen turn out 
equally good impressions, we need not be very particular 
which we follow ; in either case, however, we must take care 
not to over-saturate the plaster with water, for although the 
plaster will still set, it does not sufficiently harden. For all 
electro-metallurgic purposes, it is preferable to have plasters 
as hard as possible ; therefore, we must take care to use 
rather more plaster of Paris in our mixture than that which 
is ordinarily employed. 

The surface to which it is to be applied should be slightly 
brushed over with a very small quantity of salad oil. A 
little fluid plaster may then be poured on the cast, and with 
a hog's -bristle painting brush, thoroughly rubbed into all the 
fine parts, which will prevent the adhesion of any air-bubbles 
in the plaster which might prevent a perfect impression. 
Another portion of plaster, sufficient to give the desired 
thickness, is now to be added, and time must be given for 
the whole to set, when it should be removed from the mould, 
and gently heated over a fire to drive off excess of moisture. 
It is then found to be exceedingly hard, and ready to receive 
substances to destroy its absorption. 

The great advantage of plaster of Paris is its applicability 
to nearly all cases, for it may be employed with all metallic 
substances. - Casts can also be made with the utmost sharp- 
ness from sulphur, and it delivers so admirably from moulds 
of that substance, that the Italians use for their medallions 
almost exclusively sulphur-moulds. It is even possible to 
take a plaster- cast from a plaster-mould by previously satu- 
rating the mould with boiled linseed oil, but, however, the 
Italians do not consider these moulds form such sharp casts 
as those of sulphur. Rough and large objects are occasion- 
ally copied from plaster-moulds by simply soaking them pre- 
viously to the operation. There is no difficulty in taking 
moulds from wax, bees'- wax and rosin, stearine, spermaceti, 



PREPARATION OF PLASTER MOULDS. 135 

animal, vegetable, or, indeed, almost any organic substance. 
Plaster of Paris is . frequently coloured in various ways to 
suit the fancy of the operator, and a pretty effect is some- 
times produced by using two colours of plaster, one being 
first employed for the sunk parts of the mould, the other 
being applied over that to the flat parts, so that when the 
cast is removed from the mould, all the rilievo is of one 
colour, all the flat portion of another. 

There are various modes of filling plaster-casts to render 
them incapable of absorbing fluid. These ma"y, however, be 
divided into two classes, the application of solid substances, 
as stearine, wax, &c, by the employment of heat, and of 
substances in solution, as varnishes, &c. It may seem un- 
necessary to detail such a variety of modes for obtaining the 
same object, but as we do not always have the best at our 
command, we are glad to avail ourselves of some other ma- 
terial which will answer nearly equally well. The application 
of solid substances, rendered fluid through the agency of heat, 
is effected in every case in precisely the same way ; a minute 
description of one will, therefore, suffice for all. This mode 
of treating plaster- casts is to place them in a flat dish with 
the material, which should not exceed half the height of the 
cast, and the heat employed should be sufficient to render 
the composition perfectly fluid. The heat may be applied 
by means of a lamp, or gas-furnace, the top of a stove, or 
the hob of a fire, and the temperature should be raised a few 
degrees above the melting-point of the substance. The 
plaster previously to this operation, although well dried, will 
part with more water, which, passing off in the form of steam, 
gives an appearance of boiling. After it has remained in this 
state for a short period the cast is to be removed from the 
fluid. The temperature at which this operation is performed, 
influences the success of the process, for if taken out at too 
low a heat, a portion of the substance, be it wax, tallow, or 
stearine, will congeal on the surface of our mould, and much 



136 PREPARATION OF PLASTER MOULDS. 

impair its sharpness. If removed at too high a heat the fluid 
remaining upon the surface will rush into the pores of the 
plaster, and not sufficiently fill its texture. I like to see the 
surplus fluid on the surface of the mould gradually and 
quietly entering, taking its own time, being first absorbed at 
the circumference, and gradually lessening till the whole has 
penetrated into the mould. For different processes we 
require a more or less perfect filling. When we are only 
desirous of using our mould for simply making a metallic 
reverse, a less perfect preparation will suffice, and fifteen 
minutes' exposure to heat will be found ample enough ; if, 
however, we want most thoroughly to protect the plaster, the 
cast must be left for nearly an hour, and boiled at a higher 
heat, till the steam ceases to rise from the mould. If the 
plaster is thus thoroughly saturated, it will become semi- 
transparent, and the light of a candle may b£ distinctly seen 
through it. When the plaster is cool, a uniformly smooth, 
polished appearance will be given, and nothing will be left 
on the surface, if the operation has been properly performed. 
My experiments on plaster have been more extended than 
may at first sight seem necessary, because from the first it 
appeared to me obvious that this was the substance on which 
electro-metallurgy must be dependent for a very extensive 
application. Its mode of moulding is comparatively so sim- 
ple, so economical, and so effectual, that it is applicable from 
the smallest medallion that the genius of a Wyon can pro- 
duce, to the most gigantic statue ever constructed by the 
ingenuity of man. 

The substances used to fill plaster need not be lost, for 
after the mould has been used, by throwing it into hot water 
acidulated with dilute sulphuric acid, the substance will leave 
the plaster, and float at the top of the liquid, whilst the water 
will combine with the plaster, and remain at the bottom of 
the vessel. My attention was first directed to the use of the 
acid by Mr. De La Rue. During the immersion of the pre- 



PREPARATION OF PLASTER. 137 

pared plaster in the solution, a soap of copper is formed 
which the acid decomposes and sets free, and thus by this 
chemical trick we employ our preparing substances over and 
over again. 

There are several analogous materials which may be em- 
ployed without difficulty for filling plaster ; I generally give 
the preference to stearine, because it is cheaper and more 
cleanly than the other substances. From the best stearine 
we pass by every grade to stearine prepared by pressure, to 
hard mutton fat, and at length to ordinary tallow. This is 
well adapted for filling plaster. It is readily melted, and 
from its fluidity passes into the numerous pores of its tex- 
ture. It is as well to boil the cast for some considerable 
time in the tallow, then drain off the superfluity, and, after- 
wards, leave it in a cool place to harden. By boiling, I do 
not mean that the tallow should boil, but that the vapour 
from the plaster should give an appearance of boiling ; In 
general the hardest tallow should be selected, but good can- 
dles answer every purpose. The elaine in the tallow per- 
haps helps importantly to protect the plaster, and, therefore, 
In very large casts is valuable. 

Spermaceti also renders plaster non-absorbent, and is to 
be applied in the same way as the tallow. Spermaceti, as 
sold for candles, answers the purpose admirably. 

White wax, such as that obtained from wax candles, 
suffices very well to prevent the absorption of plaster, and 
is very easy to apply. 

Equal parts of bees'-wax and rosin previously fused, may 
also be employed with advantage to fill the plaster. The 
more rosin contained in the above composition the higher 
will be the heat required for its perfect fusion, and although 
rosin will answer by itself, yet it cannot be made to pene- 
trate more than a very short distance into the texture of 
the plaster, though a hard, clean, non-absorbent surface, can 
by this means be produced. A solution of rosin in oil of 

8 



138 PREPARATION OF PLASTER. 

turpentine may be used, but it is difficult to drive off all the 
turpentine. A mixture of rosin and grease may be also 
employed. 

JFluid substances, and substances in solution, are to be 
applied in the same way as solid materials in a state of fusion, 
the greatest care, however, being required to prevent any of 
the preparation remaining on the surface. 

The application of boiled linseed oil is another mode which 
may be practised. It should be applied to the cast until a 
very minute quantity remains unabsorbed on the surface ; it 
is then to be dried, and this is best accomplished by free ex- 
posure to sunshine. The mere hardening of the exterior film 
does not indicate a sufficient dryness for the object to be 
placed in the solution, it being necessary that the oil should 
be somewhat dry throughout. If the object be placed in the 
solution previously to its being dry, the oil will separate 
from the plaster, the solution will act upon the cast, and both 
cast and solution will be materially impaired, if not utterly 
destroyed. Plaster requires a large quantity of oil for its 
saturation, perhaps as much as half of its bulk. The casts 
should not be overdried when the oil is applied, as the oil 
does not then so readily harden. 

The same observations which apply to varnishes, balsam of 
Canada, Venice turpentine, &c, with respect to their appli- 
cation to paper, apply also to plaster articles. Of varnishes, 
the mastic and white hard are the best, but the methods 
described above are superior to those in which any of the 
varnishes are used. Experiments have been tried upon every 
other substance likely to be useful, but these it is needless to 
describe. 

I am tempted to give a table of the substances which may 
be applied to plaster, as a summary of the results of my ex- 
periments, taking into consideration their relative efficiency 
as well as cheapness: — 




GUTTA PERCHA. 139 

Tallow. Nut oil. 

Stearine. Solution of rosin in turpentine. 

Spermaceti. Balsam of Canada. 

White wax. Mastic varnish. 

Bees'-wax and rosin. White hard varnish. 

Rosin. Lac varnish, &c. 

Linseed oil. 

Sometimes we are desirous of hardening plaster, which we 
effect in two ways, either by filling it with a solution of gum 
arabic, or strong size melted. The French authors state 
that by these processes we are enabled even to take a clichee 
from plaster. 

(141.) At the present time, by far the most important 
substance which electro-metallurgists can employ for their 
casts is gutta percha. This material is quite of modern intro- 
duction, and to Dr. Montgomerie is due the honour of having 
made Europeans acquainted with its existence, as heretofore 
it was only known to certain inhabitants of Malayan forests. 
It is procured by cutting notches in the bark of the tree, from 
which a milky juice exudes, which very soon curdles. The 
tree attains the diameter of three or four feet, or even, in 
Sarawak, is occasionally said to be six feet across. The 
material is imported into this country in large square blocks, 
which contain many impurities. These blocks are cut up 
by machinery into very small shreds, and then soaked and 
boiled in water. They are then torn to pieces by other 
machines to get every foreign particle out of them, and after- 
wards the material is thoroughly kneaded together in another 
machine, at a temperature nearly of boiling water. The 
gutta percha, after this preparation, is in a state ready for 
use ; and it is only necessary slightly to cover the mould 
with soft soap, to enable a most perfect fac-simile to be pro- 
duced under proper pressure. .For small objects, the pressure 
of the thumb is sufficient, for large objects a coining-press 
must be employed, and when large surfaces are desired to be 



140 GUTTA PERCHA. 

copied an hydraulic press capable of exerting a force of many 
tons, is required to be used. 

The material was brought before my own notice, in 1844, 
by Mr. Nicholls, the original patentee ; I immediately desired 
to try it for electro-metallurgic purposes, in which it perfectly 
succeeded ; and forthwith I also tried it for splints and other 
surgical appliances. 

Gutta percha, at ordinary temperatures, is hard, but on 
being heated to the temperature of boiling water, can be 
moulded into any form. For the purpose of heating it, we 
may either soak it in boiling water, or place it in a glue-pot, 
so as to have the yielding mass free from water. In taking 
casts in it, the principal difficulty which is experienced is, to 
prevent, at times, small air-bubbles from interfering with the 
impression. 

For moulds, it is the most perfect material which possibly 
can be desired, and already is found practically to supersede 
very generally all other substances which have been employed 
for electro-metallurgy. It not only takes the most exact im- 
pression, but can be used over and over again without in 
any way being injured, or altered in its qualities. 

The Gutta Percha Company use gutta percha very exten- 
sively for the purpose of forming electro moulds, and these 
electro moulds are again extensively employed for- making 
embossed articles of gutta percha for sale, such as ink-stands, 
watch- stands, trays, vases, baskets, &c. &c. 

Gutta percha is so admirably adapted for electro-metallurgy, 
that I am not aware of one single metallic solution in which 
it may not be plunged with perfectly impunity. 

This material is a very imperfect conductor of heat and 
electricity. On account of the former property, it retains 
its heat a long time, and on account of the latter it is used to 
envelope wires to convey electrical currents under water, and 
in this way the experiment was made to convey the electric 
telegraph between Dover and the French coast, by insulating 



SULPHUR. 141 

a copper wire by placing it in about half an inch of gutta 
percha. 

It would be very desirable if the trustees of the British 
Museum would issue gutta percha casts or moulds of the 
various coins and medals in their possession. Whilst locked 
up in the strong room, they are only seen by the curious and 
dilettante antiquarians, who delight rather in the marvellous 
than the beautiful, the rare than the useful. If the collection 
of those exquisite productions has any meaning at all, it must 
be to improve the taste of the people ; and I must submit 
that the issue of casts of them at a reasonable price would 
tend to improve the taste of artisans, who have now no mode 
of cultivating it. 

(142.) The third class of substances, which comprises those 
which are acted upon by the metal reduced from the fluid, 
are few in number ; yet, unfortunately, this class contains one 
substance which takes finer casts than any other, and that is 
sulphur. The newly-precipitated metal no sootier comes in 
contact with the sulphur than it combines with it, forming a 
sulphuret, and the cast swelling enormously, is quite disin- 
tegrated. The only mode of remedying this is to coat the 
sulphur-mould with a varnish, such, for instance, as white 
hard and mastic, of which a very thin layer should be applied. 
Sulphur-casts, however, have not in my own experiments 
answered well under any treatment, and as we have so many 
other modes of taking casts, there appears to be no induce- 
ment to follow the subject farther. 

Jacobi, indeed, mentions that sulphur may be employed 
for the reception of copper, but probably it was an inadver- 
tent assertion made by classing it generally with all other 
non-metallic bodies. 

Although sulphur cannot be thus employed directly in the 
metallic solution, it makes most admirable moulds from which 
to take plaster-casts. For this purpose a stick of sulphur is 
melted in a pipkin over a lamp or fire when it is ready for 



142 SULPHUR. 

use. The heat should be applied gradually, for being a bad 
conductor, one part is apt actually to sublime and be on fire 
before another is in fusion. It is always as well to have a 
piece of old carpet at hand to place over the vessel should 
the sulphur catch fire. It may be used for most metallic sur- 
faces, taking care previously either to moisten them with 
vapour, or to oil them. It may be employed for plaster- 
casts either wetted with water or oiled, and it may be used 
to make a cast from a sulphur-mould. This is rather a nice 
process, but it is done as follows : — The sulphur-mould is 
oiled, and the melted sulphur is allowed to remain till very 
near the point of cooling, when a little is poured into the 
mould and immediately poured out again, so that the smallest 
possible quantity is left. This is allowed to cool, when a 
little more sulphur is poured in, and again poured out, and 
these processes of pouring in, and pouring out, are respec- 
tively repeated till a sufficient thickness is produced to give 
strength to the medal. Sulphur is a bad conductor of heat, 
and is apt to crack to pieces from a very slight exposure to 
that agent. Sometimes the heat of the hand will make the 
mould fly to pieces, and even, occasionally, the warmth gene- 
rated during the solidification of the plaster. It is stated 
by French authors, that this brittleness is not to be seen for 
two or three hours after it has been melted, and in that state 
it may be used for the clichee. Where appearance is an 
object to the modeller, the sulphur is coloured, either with 
vermilion, charcoal, red chalk, Prussian blue, or plumbago, 
all of which tend probably, but especially the latter, to render 
it less brittle. A very general belief exists among chemists 
that sulphur, when employed for taking moulds, is used in 
the peculiar thick state which it assumes after it has been 
heated to a considerable degree, viz., between 400° or 500° 
Faht., and plunged into water. Thus treated it remains for 
some time in a soft condition, and of a very red colour, but, 
as far as I can learn, there is no foundation for the opinion. 



BREAD-CRUMBS. GLUE. 148 

Sometimes bread-crumbs are used for moulding. The 
inner part of the loaf of bread is moistened with water, and 
thoroughly kneaded in the hand, like paste used for catching 
roach. The substances should neither be so moist as to 
adhere to the object, nor so dry as not to mould properly. 
It is. then, to be pressed upon the cast about to be copied. 
This is not a very valuable mode of proceeding, but some 
years ago it was extensively used for what were called bread 
seals. 

Glue is also, occasionally, employed for moulding. It is 
melted in the usual way by soaking it in water for twenty- 
four hours, and then boiling it at a moderate temperature — 
the glue-pot, in fact, forming a water-bath. The especial 
purpose for which it is used is to overcome the difficulty, 
which presents itself in moulding any object much undercut, 
for then the elasticity, flexibility, and general yielding nature 
of this substance are so great that the most irregular objects 
may be copied by it. Glue and whiting are much used for 
picture frames, and other similar ornaments, but this com- 
position will not prove of much benefit in electro-metallurgy. 
The last substances cannot be used as the negative pole in 
metallic solutions, but, perhaps, in some few cases they may 
be useful to the operator for taking other casts which may be 
used to receive the metallic deposit. 

(143.) Non-conducting substances may be copied or mul- 
tiplied by depositing a thin film of any conducting substance 
upon this ; and gold, silver, bronze, or copper powder, might 
be employed for this purpose. 

There is another process by which non-conducting sub- 
stances, such as animal matter, vegetables or minerals, may 
be coated with a finely-divided metal. The object is to be 
brushed over with a small quantity of the solution of any salt 
of gold, silver, or platinum, and in that state is to be exposed 
to the vapour of phosphorus obtained from the evaporation 
of either an alcoholic or etherial solution, when immediately 



144 METALLIC COATINGS. 

a deposit of finely-divided metal will take place on the 
surface. It has been supposed that this is a phosphuret of 
the metal, but if a little piece of phosphorus be placed 
in a solution of gold, silver, platinum, or copper, the phe- 
nomenon will be explained, as the respective metals will 
coat the phosphorus. The deposit of copper is particu- 
larly beautiful, and it is strange that I cannot find any notice 
of it. 

The substance to be copied may be also brushed over 
with a solution of any of the metals last mentioned, and 
exposed either to sunshine or to heat, when reduction will 
take place ; but the process is tedious, and is therefore very 
rarely employed. Any other mode by which the metals 
may be reduced, would suffice ; as, for instance, their reduc- 
tion by proto-sulphate of iron, or hydrogen gas. 

Gilding, silvering, or coppering objects by means of their 
respective leaves may be employed; yet all these modes 
are imperfect, and we have no need of any metallic covering 
whatever, as other means answer the purpose better, and are 
even more simple and cheaper. 

(144.) One of the best methods of giving a non-conducting 
substance a thin conducting layer, is by the application of 
carbon, either by charcoal or powdered black-lead. It is only 
necessary to brush these substances over the object till the 
thinnest film is obtained, as that will be amply sufficient 
for the purpose for which it is wanted. The black-lead is the 
best, on aocount of its peculiarly unctuous nature, which 
enables its application to be made with the greatest ease, 
either by a camel's hair or hog's bristle brush, according to 
the nature of the substance to be covered ; care must, how- 
ever, be taken, that the interstices between the fine lines are 
not blocked up, as this would of course render the duplicate 
imperfect. Occasionally, there is some difficulty in making 
a thin film adhere to the surface, but if it be an object 
where perfect sharpness is not indispensable, a small quantity 



BLACKLEADING. 145 

of varnish may be applied ; a proceeding which is suitable 
to earthenware. Sometimes a little spirit of wine may be 
used, when a cast is capable of being acted upon by that 
fluid, as sealing-w r ax, but great care must be taken not to 
render the surface rough. Upon many substances, the black- 
lead may be made to adhere by simply breathing upon the 
object. In whatever manner we cause its adhesion, it is 
important always to bear in mind, that it is of more conse- 
quence that a smooth polished surface of black-lead be ex- 
posed, than a thick and rougher coating. 

The different opinions which are entertained, as to the 
applicability of black-lead for this purpose, are owing entirely 
to the fact, that great difference exists between samples of 
that article ; for if it be not really carbon, it is absolutely a 
non-conductor, and I have found a number of pieces totally 
inactive, while others were most excellent conductors. The 
action or inaction of different pieces, before grinding, is not 
at all dependent on their hardness, for I possessed a piece of 
that variety, called by the pencil-makers rock, which com- 
pletely annihilated the teeth of three of the saws with which 
I attempted to cut it. I then sent it to a celebrated me- 
chanic, for the purpose of having it sawed, but he succeeded 
no better than myself; in fact, nothing but a diamond w r ould 
have made any impression upon it, and yet it was one of 
the best pieces for voltaic purposes which I ever possessed. 
Sometimes, on the contrary, hard pieces are of no value, 
whilst soft ones are excel] en tly adapted for galvanic pur- 
poses. There is no method but direct experiment, by which 
the conducting quality of any particular sample of black-lead 
can be ascertained. There are not two shops where it can 
be bought alike, so much being either naturally bad, adul- 
terated, or ill-prepared. Perhaps the best test of good black- 
lead is to take a pinch between the finger and thumb, and 
press it, when, if good, it will cake together and adhere. If 
charcoal be employed, it should be well burnt, and in the 

8* 



146 COMPARISON BETWEEN THE DIFFERENT SUBSTANCES. 

finest possible state of division. The prepared charcoal of 
the shops exists in the state of an impalpable powder, but it 
is difficult to apply it. 

(145.) Of all these various methods, none is, in my opinion, 
at ail comparable to good black-lead. The thinness of the 
coating is such, that it is not sufficient of itself to carry the 
voltaic current (for a layer so thin as only to be visible by 
reflected light is sufficient), but this thin layer so favours the 
extension of the copper laterally, that the whole surface 
speedily becomes coated. It is very interesting to trace the 
layer of copper extending itself over any object. For this 
purpose, a piece of black sealing-wax, coated with black-lead, 
answers best, as the difference of colour renders its mode of 
precipitation very evident. It will be seen that the copper 
grows, perhaps, from some point of the wire, on to the black- 
lead, and gradually extends itself laterally till the whole is 
infilmed bv the metal. 



147 



CHAP. III. 

ON THE LAWS REGULATING THE REDUCTION OF THE METALS. 

Metals capable of being reduced by the voltaic fluid, 146. States in 
which they exist, 146 — 148. Law for the reduction of the metals as 
a black powder, 148. Law for the reduction of the metals in crystals, 
149. Law for the reduction of the metals in the regular state, 150. 
Cause of the reduction in the states, 151. Mode of producing them, 
153 — 159. Mode of obtaining the black powder, 159. The crystal- 
line state, 160. The reguline state, 161. The same results obtainable 
by the single-cell apparatus, 165. Time required for the deposition of 
the metals, 167. 

(146.) When we subject any metallic solution to the action 
of the voltaic current, the metal itself will be reduced, al- 
though not always in the same state. Thus, if we dip a 
knife into a strong solution of sulphate of copper, bright 
metallic copper will be deposited ; but if we use a piece of 
zinc, a black mass of copper will be thrown down. Again, 
introduce a piece of zinc into an ammoniacal solution of sul- 
phate of copper, and the reduced copper will be bright, whilst, 
if we dip iron into a very dilute and acid solution of the sul- 
phate, black metal will be reduced. The learned are divided 
in their opinions as to whether the metal, in these cases, is 
reduced by single elective affinity, as they term it, or 
whether a galvanic action causes the deposit. Perhaps, in 
the first instance, the iron or zinc having a greater affinity 
for the acid and oxygen of the salt than the copper, combines 
with it, forming a sulphate, whilst the copper is thrown 
down ; but as soon as the first portion of copper is deposited, 



148 ON THE LAWS REGULATING THE 

a galvanic battery is formed, which increases the action still 
farther. Be this, however, as it may, the fact I wish to im- 
press in this place is, that the same metal may, under different 
circumstances, be reduced in different states. 

Having shown that the same metal may be reduced in 
different states, we are next led to ascertain experimentally, 
what are the circumstances which tend to vary these con- 
ditions. We, accordingly, procure a galvanic battery and 
connect it with two platinum poles, which we place in a 
vessel to serve as the precipitating trough. In this trough 
we place a saturated solution of a metallic salt, for instance, 
copper, when on examination, if the battery possesses but 
feeble power, we shall find that crystalline copper will be 
deposited; if, however, we dilute this solution with twice, 
thrice, or four times its bulk of water, the metallic deposit 
will assume a very different aspect. It will then be aggre- 
gated in a flexible state, which, to prevent circumlocution, I 
shall term the reguline deposit. If we now dilute this same 
solution to an infinitely greater extent, the metal will still 
be reduced, but in the form of a black powder ; a deposit so 
fine that the highest power which the skill of a Powell, or a 
Ross, can impart to the microscope, will not enable the eye 
to discover the form of the minute particles of which it is 
composed. Almost all metallic solutions may be substituted 
for that of the sulphate of copper, and the experiment will 
show nearly the same result, namely, that the strength of the 
metallio solution very materially influences the nature of the 
deposit. If this fact is really correct, we ought to be enabled 
to obtain on one negative pole several ki;iJs of deposit, were 
it but possible to make a solution of unequal strength. Now 
we can make a solution of unequal strength by placing the 
crystals of metallic salt at the bottom of a tall glass vessel, 
and pouring upon it some conducting fluid, for, after a little 
time, if the liquid be examined, the lower part will be found 
to be of the most intense colour, and contain most metallic 



REDUCTION OF METALS. 140 

salt, whilst the shade will vary to the top from that portion 
containing scarcely any. For this experiment a solution of 
sulphate of copper will answer perfectly well. In it we 
place our electrodes, which may be of copper, and con- 
nect them with a single galvanic battery. At the pole 
joined with the zinc of the battery, copper will presently 
begin to be deposited ; black powder at the top, reguline 
metal a little below the centre, and crystalline copper at the 
bottom. If we stir the solution up and thoroughly incor- 
porate it, a uniform metal will be deposited at every point. 
This experiment confirms our previous view, that the power 
being equal, the condition of the metal will depend upon the 
strength of the solution. If we examine the converse of the 
experiment, and take a solution of sulphate of copper (which 
should be acidulated to make it a better conductor), and use 
successively, first one very small battary, then two or three 
batteries arranged in a series, and, lastly, a very intense 
battery, we shall find that with this self- same solution we 
can obtain by these means, first a crystalline, then a reguline, 
and, subsequently, a black deposit. This experiment shows 
that the amount of electricity passing in any given metallic 
solution also influences the state of the deposit. From 
variation of the strength of the metallic solution causing 
reduction of metals in different states, and from variation in 
the amount of the power also influencing the state of the 
metal, we are forced irresistibly to the conclusion, that to 
obtain with certainty any particular metallic deposit, we 
must regulate the galvanic power actually passing to the 
strength of the metallic solution. This is the fundamental 
principle — the very essence, in fact, of electro-metallurgy; 
and when we consider from how many causes the one, the 
other, or both may be interfered with, we begin at once to 
obtain an insight into the difficulties which the operator 
must incur in conducting his operations. This grand prin- 
ciple applies to all metals, and even to all the salts of each 



150 REDUCTION OF METALS AS A POWDER. 

metal ; but as every metallic sort varies in its conducting 
power, and in the facility with which it yields its elements, 
great choice is given to the workman to select the salt most 
applicable to the particular process which he is desirous of 
performing. 

(147.) The laws which regulate the deposit of every metal 
appear to be the same, and although very simple, yet they 
have cost me much labour for their development. The pro- 
perties of which I have here to speak are strictly those 
which relate to the quality of the metal, which is so mate- 
rially influenced by various circumstances. The reduced 
metal may be precipitated in three different ways ; as a 
black powder, as a reguline metal, (or, in other words, a 
metal having the properties of ductility and malleability,) 
and, lastly, as a crystalline deposit. Between these there 
are, indeed, other intermediate states, or mixtures of two 
different states, of which we shall hereafter take notice. 

(148.) Law I.— The metals are invariably thrown down 
as a black powder, when the current of electricity is so 
strong in relation to the strength of the solution, that 
hydrogen is freely evolved from the negative plate of the 
decomposition cell. 

The different states which reduced metals assume, as well 
as the different varieties of each state, appear to be nothing 
but a difference of aggregation of the minute metallic par- 
ticles of which they are composed : metals deposited in a 
black powder are, probably, in an infinite state of division ; 
then, as a variety of this amorphous mass, we have a spongy 
material, resembling, more or less, the colour of the metal, 
but the particles of which are still so fine, that it may be 
moulded with the fingers into any shape we desire. As 
another variety of this deposit, the spongy mass may be 
aggregated hero and there into hardish lumps, interspersed 



REDUCTION OF METALS AS A POWDER. 151 

in the sponge, and this condition may be so far increased 
as to give rise to the form which is termed the sandy deposit. 
Such are the varieties of the pulverulent deposit, the first 
class of metallic reductions, comprising black powder, sponge, 
and sand. 

The cause of these varieties appears perfectly obvious, for 
hydrogen and copper are deposited at the same time. In 
a former part of the work we had to treat at great length 
upon the power of adhesion which this gas possesses, and if 
in this place we apply the same fact, we shall see that it 
will sufficiently account for every variety of the pulverulent 
deposit. If the hydrogen is evolved in very large quantities, 
we can easily imagine that it would envelope each ultimate 
particle of the reduced metal, and prevent the cohesion of the 
neighbouring atoms. In confirmation of this rationale, the 
metal in this state, notwithstanding its usual colour, is uni- 
formly black, a fact perfectly in accordance with the pro- 
perties of light. Any substance in infinite division must of 
necessity be black, from its not having breadth enough to 
reflect a ray of light, which requires certain definite dimen- 
sion, which philosophers have measured. If the hydrogen 
is evolved in smaller quantities, we can easily conceive that 
some of the atoms of the metal would be aggregated together, 
forming the spongy deposit; if, on the contrary, the quantity 
of metal deposited far exceeds the quantity of hydrogen 
produced, we can easily see that more metallic particles 
would be in conjunction, and, therefore, the deposit would 
be much firmer. If, lastly, the hydrogen is almost nothing, 
we can also understand that the particles of sand would be 
still farther increased in size. Metals of all colours and 
properties exhibit the same phenomenon * even silver, plati- 
num, &c, which are usually white, gold, which is yellow, 
and copper, w r hich is red, together with other metals, obey 
this law, all being easily reduced as a black powder. 



152 REDUCTION OF METALS IN CRYSTALS. 

(149.) Law II. — Every metal is thrown down in a crys- 
talline state, when there is no evolution of gas from the 
negative plate, or no tendency thereto. 

When I speak of no tendency to the evolution of the 
hydrogen, I mean that the strength of the metallic solution 
is so great that either electricity of a much greater tension 
must pass, or the solution must be rendered of more easy 
decomposition, before gas would be evolved from the elec- 
trical power employed. 

This is, in fact, in strict accordance with the generally 
known properties of bodies, for we find, universally, where 
bodies are deposited quite at their ease, and very slowly, that 
they have a tendency to assume each for itself some peculiar 
and definite form. In the deposition of a salt, for instance, 
if it is suddenly precipitated, it always presents itself as a 
fine powder, which would appear to be almost in the ultimate 
state of division ; but if the deposit takes place very slowly, 
it will assume some peculiar form. Nothing can be more 
complete than the analogy between the crystallization of a 
salt and the crystallization of a metal, for both agree in their 
atoms requiring sufficient time to arrange themselves in their 
own peculiar way. The crystalline condition is not very 
generally adapted for the purposes of the arts, because the 
sides of each separate crystal do not firmly adhere to its 
neighbour, but it is most admirably suitable for coating a 
reguline deposit, adding a beauty and lustre which it is im- 
possible to give in any other way. If, indeed, the crystals 
are very slowly formed, each one will have so slight an ad- 
hesion to its neighbour, that a piece held by its edge will 
break from its own weight ; and we may even increase this 
property to such an extent that only solitary crystals may, 
here and there, be deposited. In the crystalline state, the 
brittleness of the metal would appear to be caused by the 
liquid wetting each separate crystal, and the interval caused 



REDUCTION OF REGULINE METAL. 153 

by the film of water in the mass of copper, would account 
for the very slight adhesion that is found to exist. 

(150.) Law III. — Metals are reduced in the reguline 
state when the quantity of electricity in relation to the 
strength of the solution is insufficient to cause the pro- 
duction of hydrogen on the negative plate in the decom- 
position trough, and yet the quantity of electricity very 
nearly suffices to induce that phenomenon. 

In fact, the reguline state is obtained in the greatest per- 
fection when hydrogen is not far from the point of evolution, 
but yet none is really given off from the negative metal. 

(151.) The reguline metal, possessed of the properties of 
flexibility, malleability, and elasticity, seems to be produced 
by such an arrangement of the ultimate particles of the de- 
posited metal, that, being thrown down in exact apposition, 
they form a regular mass, presenting frequently at the back 
of the object, a similar uniform surface to that seen at the 
front. When we perceive in ordinary metallurgic operations 
that the same metal may vary much in its properties, that at 
one time it may be flexible, at another elastic, and at a third 
brittle ; and when we farther perceive that the density of the 
same metal may vary, that a cubic inch at various times 
may even differ in weight, we must not be surprised to find 
that reguline metal formed by electro-metallurgical processes 
may vary in the same way; and, indeed, we do find that 
differences of the same nature really occur. To attempt the 
explanation of these things, would lead us far beyond human 
knowledge, and carry us to the properties of the ultimate 
atoms of substances, for, doubtless, these differences are 
produced by variations in the arrangement of these particles ; 
how otherwise can we account for the compression caused 
by hammering a solid body, or the increase of volume from 



154 REDUCTION OF REGULINE METAL. 

annealing it. To obtain, however, the reguline metal in great 
perfection, we should carry on our process with such celerity 
in relation to the strength of the solution, that at every point 
of the negative surface, or that at which the metal is depo- 
sited, the action should be uniform, and atom by atom of the 
metal should be so quickly thrown down, that no time is 
allowed for the particles to follow their own fancies and 
arrange themselves in crystals. There are, indeed, many 
little circumstances which interfere with the apparent density 
of the reguline metal ; thus the ultimate particles appear to 
be thrown down closer together at a low than at a high tem- 
perature. 

(152.) Dismissing theories, however, we must remembei 
these facts : that the electric power in any solution, when 
barely sufficient for the production of hydrogen, causes the 
reduction of the metal in a malleable and ductile state • that 
the electric power, when not nearly sufficient to cause th< 
appearance of the gas, throws down the metal in crystals 
and, lastly, that the pulverulent deposit is produced when 
there is evolution of the gas. 

(153.) A very brief examination of our laws will show that 
the two properties of galvanic batteries must operate in an 
important manner in regulating these results, and, accord- 
ingly, we find that they are materially modified by the size 
and power of the battery. The regulation of intensity is, 
perhaps, of the greatest importance ; for, on the one hand, 
economy requires as few cells as possible, and, on the other 
hand, other circumstances require more. Whenever it is 
possible, the fluid to be decomposed should act on the positive 
pole of the fluid. Thus, in the decomposition of salts of gold, 
silver, iron, lead, tin, and copper, we use in the decomposition 
apparatus, positive poles of these respective metals. This 
enables us to conduct our precipitations with a single cell, 
which, with my battery, enables us to obtain any given 
amount of work at the smallest possible cost. During the 



EFFECT OF INTENSITY ON THE DECOMPOSITION. 155 

decomposition, the metals mentioned above are dissolved pre- 
cisely to the same amount as that to which the new deposit 
is obtained if no interference takes place. The solution is, 
in the same way, always of the same strength. 

(154.) The degree of action of the fluid on the positive 
poles, or rather of the oxygen and acid transferred to the 
positive pole, varies with every salt of the same metal. To 
regulate the action equally in different cases, acids, either of 
more or less oxydizing power, or in greater or less quantity, 
are added to the metallic solution to be decomposed. An in- 
crease or decrease of the temperature influences, materially, 
the intensity required for different salts, because at a higher 
temperature the current passes with more facility, and the 
action on the positive pole is more energetic. These minutiae 
have hereafter to be fully discussed ; but here I wish to 
point out, that, when possible, one cell only of the battery is 
to be used, and where this is rather deficient in intensity, 
a compensation should be obtained by adding to the metallic 
solutions acids of more or less affinity for the positive pole, 
according as that may be required, so that, instead of in- 
creasing intensity, we lessen resistance. 

(155. ) For those cases where we use a positive pole or 
anode made of platinum, we are compelled to obtain in- 
creased intensity by employing a more extensive series of 
batteries. In these cases, we must use as many cells as will 
decompose water ; and three or four will in general be amply 
sufficient. Beyond the mere capability of decomposing water, 
I cannot perceive that increment or decrease of intensity, 
as a general use, is of material importance, and the regu- 
lation of the quantity must then be made the subject of 
attention. 

(156.) The quantity of electricity passing in any fluid will 
depend, caeteris paribus, upon the distance between the elec- 
trodes, the extent of surface they expose to the fluid, or their 
relative size one to another. These properties have been 



156 EFFECT OF QUANTITY. 

already described, when treating of galvanic batteries in 
general, and do not, therefore, require further description in 
this place. However, a different quantity of electricity is 
required for every variation in the strength of the solution ; 
as any increase of the metallic salt requires a corresponding 
increase in the quantity of electricity ; and the converse is 
equally true. 

(157.) The quantity of electricity passing in a solution of 
copper, curiously influences the state of the crystals, for tnere 
are two varieties of this deposit, one of which arises from a 
deficiency of quantity, in relations to the strength of the 
solution, and in this state the new plate of metal is like an 
aggregation of sand, in fact, like common sandstone, the 
particles having no more cohesion or consistence. In this 
state, the plate of metal is in the utmost state of brittleness, 
and this, we must recollect, is produced by too small a quan- 
tity of electricity in a strong metallic solution. The second 
variety of the crystalline state of metals arises from a large 
quantity of electricity, in relation to the size of the plate ; 
thus, by using a very large positive pole, connected with a 
battery of feeble intensity, and by employing, at the same 
time, a strong solution, large crystals, possessing the utmost 
degree of hardness, will be thrown down. 

(158.) To carry into effect these general laws as we may 
have occasion for them, let us recapitulate the circumstances 
which may affect them. For this purpose I snail divide the 
apparatus into its two natural divisions : the precipitating 
trough and the battery : the variations which may occur 
in each being placed under their respective heads. Strictly 
speaking, as the battery and precipitating trough are regu- 
lated by the same principles, the variations in each should 
be alike ; but, practically, the arrangement annexed will be 
found most convenient : — 






MODE OF OBTAINING VARIOUS DEPOSITS. 



157 



DECOMPOSITION TROUGH. 



Uniform strength of metallic solu- 
tion. 

Temperature of ditto. 

Conducting power of ditto. 

Size of positive pole. 

negative pole. 

Radiation between the poles. 

Approximation of the poles. 

Facility of removal of the newly - 
formed salt. 



GALVANIC BATTERY. 



Primitive force of battery. 
Size of plates of ditto. 
Approximation of the plates. 
Conducting power of exciting fluid. 

Ditto, of connecting wires. 
Facility of removal of the newly- 
formed salt. 



By a glance at this table, we perceive eight variable cir- 
cumstances in the precipitating trough alone, which may 
change a hundred times during the day, opposed to six 
variable conditions in the galvanic battery. When we fur- 
thermore consider, that each of these circumstances is not 
only susceptible of every variety of alteration, but that in 
each part of the fluid the condition may vary, we per- 
ceive that the changes to which every metallic salt may be 
subjected are infinite. Disheartening as this view of the 
most favourable process by which our operations can be con- 
ducted certainly appears, let us not be overwhelmed with 
the difficulties presenting themselves, but rather rejoice that 
this mode of working in metals by unknown agents will 
never be subjected to blind experience nor to ignorant 
practice, but will require the constant superintendence of 
the mind of man, raising electro-metallurgy far above the 
lower arts. 

If we examine the above table in reference to the funda- 
mental principle of electro-metallurgy, — the regulation of 
the quantity of electricity to the strength of the metallic 
solution — we find that the strength of the solution being 
fixed and rendered as certain as possible, all the other con- 
ditions relate only to the quantity of electricity which is 
allowed to pass through that solution. In any fixed metallic 



158 MODE OF OBTAINING VARIOUS DEPOSITS. 

solution the deposit is influenced by the amount of electricity- 
passing, according as these conditions in the trough or 
battery are varied. The more these conditions are exalted, 
the greater the quantity of electricity which will pass: the 
more they are depressed, the less the amount of the voltaic 
force that will traverse the solution. 

In those instances in which the electro-magnetic and mag- 
neto-electric power are substituted for the power derived 
from the galvanic battery, the deposition of metal is obe- 
dient to similar laws, and is influenced in the same manner 
in the decomposition trough. When we desire to lessen the 
power from the machine, we may most conveniently effect it 
by causing the keeper to revolve more slowly, and in some 
cases by lowering the magnetical power. 

(159.) In any given solution we may increase the disen- 
gagement of the hydrogen so as to cause a black deposit, by 
increasing the intensity and quantity of the battery ; by a 
series ; by diminishing the size of the negative pole and en- 
larging the positive electrode in the decomposition trough ; 
by approximating the electrodes or poles ; or, lastly, by 
increasing the heat. All these conjointly, or any of them 
separately, will favour the increase of electricity, as they will 
increase the quantity of hydrogen evolved. 

For any given size of the negative plate we can obtain a 
black deposit, by increasing the intensity and quantity of the 
battery ; by increasing the positive electrode in the preci- 
pitating trough ; by diminishing the quantity of metallic salt 
in solution, at the same time adding to its acid ; and by 
approximating the poles. 

With any given battery (provided it will decompose water) 
we can obtain a black deposit, by diminishing the size of the 
negative pole in the precipitating trough ; by increasing the 
size of the positive; by approximating them, and by rendering 
the metallic solution very weak with dilute acid. 

(160.) To obtain a crystalline deposit with any given solu 






CRYSTALLINE DEPOSIT. REGULINE DEPOSIT, 159 

tion, we diminish the quantity of electricity, as well as the 
intensity derived from the battery. We increase the size of 
the negative pole in the decomposition trough, diminish the 
positive, and separate them. 

With any given negative phite in the trough we can 
obtain a crystalline deposit by diminishing the power of the 
battery, by saturating the solution in the precipitating trough 
with the salt, and taking care that it is not acidulated. 
The positive plate may be diminished, and separated from 
the negative. 

With any given battery we can obtain a crystalline de- 
posit, by strengthening the saline solution in the decompo- 
sition trough, and not acidulating it ; by increasing the 
negative electrode, diminishing the positive, and separating 
them. 

(161.) To obtain the metal in the reguline state is, how- 
ever, our great object, and to obtain the exact point of evo- 
lution of the hydrogen is important and difficult. With any 
given metallic solution, if we find the hydrogen too abundant, 
we may either increase the negative pole in the decomposition 
trough, or diminish the positive, which will suffice in 11 any 
cases. But in some operations we are desirous of having the 
electrodes of the same size, and then we diminish the size of 
the plates of the battery, or the strength of its charge ; for 
instance, I sometimes use my battery charged with water 
and a faint trace of acid. Again, in other cases we are de- 
sirous to increase the rapidity of the process, and then the 
evolution of hydrogen in the trough will be diminished 
by increasing the quantity of metallic salt in solution, a mo- 
dification which will answer every purpose. Variation in 
the distance between the poles in the trough will be found 
sufficient, in many cases, to regulate the evolution of the 
hydrogen. 

The temperature at which the solution is kept will also 
materially influence the same phenomenon, for the electric 



160 REGULINE DEPOSIT. 

fluid passes to a much greater degree at a high than at a 
low heat. 

The converse of all these procedures is equally applicable 
to those cases where the hydrogen is deficient. By regu- 
lating the strength of the metallic solution, and adding more 
or less dilute acid, the evolution of the hydrogen, in any bat- 
tery (provided it be sufficiently intense to decompose water), 
will be perfectly under control. 

The student in electro-metallurgy will at once perceive 
that these three last voluminous directions are perfectly un 
necessary to any person thoroughly conversant with the 
properties of galvanic batteries and the doctrine of resist- 
ances, for they are but a recapitulation of what has been 
already so fully considered in the book on Galvanism. To 
recapitulate, therefore, in a few words : when we desire to 
cause the powdery deposit, we diminish all resistances to the 
passage of the electric fluid ; when we desire to cause the 
crystalline deposit, we increase all the resistances ; and, lastly, 
to cause the reguline metal, we must cautiously regulate the 
resistances according to the strength of the metallic solution. 

(162.) Thus, with any amount of salts in solution, with 
any-sized negative plate, with any-sized battery, and at all 
temperatures, we can obtain the reduction of any metal in 
any state we please. It is true that this excessive refinement 
has hardly been carried to each salt of every metal, yet the 
principles have been so far accurately demonstrated with 
such a number of them, as to leave no doubt of their general 
truth and value. 

It has accidentally been discovered that when a few drops 
of bi-sulphuret of carbon are dropped into a large quantity 
of certain solutions, the metal deposited has a particularly 
brilliant appearance. This property has been patented, and 
has been found by various electro-metallurgists to be of 
great value to the arts. The theory of its action is totally 
unknown : but doubtless, when worked out, may lead to im- 



REGULATION OF GALVANIC POWER. 161 

portant discoveries, and is therefore well worthy the attention 
of the experimenter. 

In detailing my observations upon the deposition of metals, 
I have assumed that we are working with pure salts ; for if 
twc or more salts are mixed together, the deposition obeys 
th 3 laws which will hereafter be detailed when speaking of 
allots. 

(1:3.) To regulate the galvanic power to the strength of 
the solution will henceforward be my constant theme through- 
out the concluding part^of this volume. Having once begun 
I shall continue and end with it, that this important point 
may be so firmly impressed upon the minds of those who 
practise electro-metallurgy, that they may conduct their pro- 
cesses — not by chance, nor blind experience, but — by un- 
erring and never-failing principles ; that when the operator 
desires to luake alterations in his battery, his trough, or his 
solution, h*a will at once be possessed of the secret of adapt- 
ing every ether circumstance to attain the end he requires. 
To regulate also the uniform strength of the solution by the 
proper diffusion of the newly-formed metallic salt, must also 
be my continued advice ; that success may crown the labours, 
pleasure the success, and profit the pleasure derived from the 
practice of electro-metallurgy. The want of an uniformity 
of strength in the metallic solution perplexes the tyro in 
electro-metallurgy more, perhaps, than any other circum- 
stance ; for after having mixed a solution of definite strength, 
and having taken the greatest pains that the positive and 
negative surfaces should be under the same conditions in 
every part, he is surprised that frequently, in the same solu- 
tion, he has every variety of deposit. He, perhaps, in his 
disappointment, declares that electro-metallurgy depends on 
chance ; but let him only particularly examine the state of 
the solution, and he will find that, from various causes, the 
uniformity has been destroyed. At one place the acid will 
be in excess, and in another the metallic salt. Rays from 

9 



162 SINGLE CELL APPARATUS. 

the sun may have heated the upper part of the solution, 
which would still remain at the top, as the hotter part being 
lighter would not cause that circulation which is necessary 
for the heating of fluids. Sometimes, indeed, the metallic 
salt would seem to subside to the lower part of the decompo- 
sition vessel, leaving the upper part comparatively unsatu- 
rated. In the description of electro-metallurgical apparatus, 
the best method of regulating the uniformity of the strength 
of the solution has been already considered : we need not, 
therefore, further allude to it in this r>lace. 

(164.) In detailing the above laws, the battery has been 
more especially alluded to, because we can, by its means, 
regulate most exactly the quantity and intensity of the cur- 
rent. The same principles apply to the cases in which the 
metal on which the reduction is to take place is made the 
negative plate to a piece of zinc enclosed in a porous tube, 
but we cannot adapt this with that nicety which the battery 
admits. 

(165.) The quantity of electricity in a single-cell appara- 
tus may be increased by enlarging the zinc plate ; by ap- 
proximating it to the negative ; by diminishing, as much as 
possible, any resistance offered ; by the use of diaphragms, 
and by adding to the acid of the solution which acts upon 
the zinc. The quantity of electricity may, in like manner, 
be diminished by adopting an opposite course of proceeding. 
In the use of the single-cell apparatus, as in that of the 
battery, the strength of the metallic solution to be decom- 
posed will materially influence the quantity of electricity 
required for its reduction. The neutrality of the solution, 
the acidity, or the nature of acidity, will operate in a 
similar manner. The different conditions have been suffi- 
ciently adverted to, when speaking of the effects of those 
circumstances in the use of the battery. The above facts 
alone are sufficient to make forcibly apparent the imperfection 
of the single-cell apparatus, and the superiority of the process 



MICROSCOPICAL CHARACTERS OF DEPOSIT. 163 

by the battery. The application of iron, tin, and lead for 
the production of the voltaic force, must be subjected to the 
same regulations as zinc. In these cases, however, the elec- 
trical power generated is so low, in comparison with that 
derived from zinc, that there is little fear of obtaining a super- 
fluity of the voltaic force, but, on the contrary, such a feeble 
production of that agent requires us to facilitate its passage, 
by affording as few resistances as possible. 

Mr. Warren De la Rue has investigated the microscopical 
characters of el ectro -metal] urgic deposits. From his re- 
searches he believes that these depositions are all crystalline, 
and the quality of the deposit is owing to the extent of the 
separation of the crystals. In fact, he states that it is but a 
tissue of crystals interlacing, but not adhering, and contain- 
ing within its texture a vast mass of pores. There is no 
question that his statement is perfectly correct in most cases, 
and it appears to me that these deposits are, in every respect, 
similar to different varieties of ice. In the first place, we 
have the beautiful flexible ice, which possesses great strength, 
and which is analogous to our reguline metal ; then we have 
ice built up of larger and smaller crystals; then we have that 
rotten compound of half snow. It is practically known to 
dealers in ice, that some varieties are more compact than 
others : so with electro deposits, there is no doubt that some 
forms are more solid than others. This difference, doubtless, 
depends upon the mode of aggregation of the particles. In 
electro deposits the particles have a great tendency to 
aggregate towards the positive pole, and then liquid is re- 
tained between the crystals. In some cases the growth ap- 
pears to take place laterally, when the metal has a polished 
appearance during deposition, and then the aggregation is 
more complete, and no crystals are seen on the surface. 

In some of my experiments I have seen crystals of copper 
start towards the positive pole, two inches long, where intense 
batteries have been employed ; but with regard to tin and 



164 EFFECT OF TIME ON THE DEPOSIT. 

lead, this formation of crystals is one of the greatest diffi- 
culties with which we have to contend. As we find this 
tendency of the crystals to start from the negative to the 
positive pole, where the current of electricity manifests 
much intensity, it would be as well to have, in such cases, 
batteries of the lowest possible intensity, or divide that inten- 
sity amongst a series of precipitating troughs. 

(166.) There are certain peculiarities appertaining to each 
metal, and even to each salt of the same metal. Each de- 
mands somewhat different management, depending upon the 
circumstances under which the reduction of the metal takes 
place. The necessary variation in the modes of operating 
will be considered in the next chapter. 

(167.) And now let us consider the influence which time 
exerts over these processes. Is it necessary, as all authors 
have asserted, that the voltaic precipitation should go on 
slowly ? The fundamental laws which regulate the precipi- 
tation of metals exclaim at once, by no means ! For if the 
electric power be regulated to the strength of the solution, 
precipitation may take place at a rapid rate. In fact, we 
shall hereafter show that the reduction of the metals may be 
more speedily effected than at first sight appears possible, 
because the deposition is amenable to the same laws 
whether it takes place slowly or rapidly, because the quality 
of the metal depends on the regulation of the quantity 
of electricity to the strength of the metallic solution. 



165 



CHAP. IV. 

ON THE REDUCTION OF THE METALS. 

Introduction. Formation of salts, &c., 168. Reduction of Platinum, 169. 
Gold, HO. Palladium, 171. Iridium, 172. Rhodium, 173. Os- 
mium, 174. Silver, 175. Nickel, 176. Copper, 177. Zinc, 178. 
Cadmium, 179. Iron, 180. Tin, 181. Lead, 182. Antimony, 183. 
Bismuth, 184. Uranium, 185. Arsenic, 186. Tungstic acid, 187. 
Cobalt, 188. Manganese, 189. 

(168.) In what part of electrical science are we not in- 
debted to Faraday 1 He has increased our knowledge of the 
hidden and unknown to such an extent, that all subsequent 
writers are compelled so frequently to mention his name and 
quote his papers, that the very repetition becomes monoto- 
nous. However humiliating it may be to acknowledge so 
great a share of successful investigation to one man, yet 
when we come to describe the electro-chemical decomposi- 
tion of metallic salts, we are forced to render our feeble 
tribute for his communications on the extended subject of 
voltaic decompositions. He has shown that we can only re- 
duce metals on the negative pole of a galvanic battery from 
a solution which contains them in combination with some 
other substance : for if we galvanize a metal in the ele- 
mentary state for ever, the voltaic power would have no 
property to move it to either electrode. He has also proved 
that not only must the metal be combined in the definite 
chemical proportion to form a metallic salt, but, in order 
that it may be decomposed, it must be in that peculiar phy- 
sical state called liquidity, or fluidity. It is not, indeed, 
necessary that the salts themselves should be liquid, for if 
dissolved in any other fluid they will still yield up their 



166 THE FORMATION OF SALTS. 

elements to the electric principle. From these considera- 
tions it is manifest, that, whenever we are desirous of work- 
ing in any particular metal by the galvanic fluid, it is ne- 
cessary first to form some compound of that metal which is 
soluble in some fluid. The substances with which metals 
most readily combine are oxygen, chlorine, bromine, iodine, 
sulphur, cyanogen, and, in some cases, even hydrogen. The 
compounds of chlorine and bromine are generally soluble in 
water, giving rise to that class of salts called muriates, or 
hydrobromates, and are then at once fit for use. The com- 
pounds of iodine are, as a class, insoluble themselves, though 
with hydriodate of potash they frequently form soluble com- 
pounds. 

Of the metallic fluorides I have had but little experience, 
and, probably, they will not be much employed for electro- 
metallurgy. 

Most of the compounds of metals with oxygen, or oxydes, 
are insoluble themselves in water, but become soluble when 
further combined with acids, alkalies, and certain neutral 
salts. Thus, oxyde of copper, which is absolutely insoluble, 
readily dissolves in sulphuric acid, in ammonia, or cyanuret 
of potassium, &c. Were I to enter fully into these matters, 
the reader would find himself troubled with an extensive 
work on chemistry, instead of an epitome of electro-metal- 
lurgy, and, therefore, I can only add a very short list of sub- 
stances which, combining with oxydes, render them soluble 
in water : — 



Bromine. Ammonia. 

Chlorine. Potash. 

Fluorine. Soda. 

Sulphuric acid. Bitartrate of potash. 

Nitric acid. Muriate of ammonia. 

Acetic acid Hypo-sulphite of soda. 

Tartaric acid,— indeed nearly Sulpho-cyanuret of potassium, 

all the other 200 acids. Cyanuret of potassium. 



FORMATION OF SALTS BY MAGNETISM. 167 

Metallic salts are generally formed in three ways. The 
first, where the metal itself is added to the acid and water ; 
when the latter is decomposed by the metal, the hydrogen 
being evolved, and the corresponding equivalent of oxygen 
combining with the metal produces an oxyde which again 
unites with the acid to form the metallic salt. The second 
mode of forming metallic salts, when the metal cannot decom- 
pose water, is, to add the oxyde already prepared to the acid, 
and, if necessary, digest it at a moderate temperature- The 
last mode of making metallic salts is, to take a solution of 
the acid which we desire to be the radicle of our salt, and 
place a very large positive pole of the metal desired to form 
the base at the lower part of the fluid, and connect it with 
the terminal silver (s) of a series of batteries (two, three, or 
four, according to circumstances). For the negative pole 
we use a small piece of metal, and connect it with the ter- 
minal zinc of the battery (z). 

In this way we very readily and conveniently make our 
saline solution ; for the metal 
being dissolved is retained prin- Fig. 29. 

cipally at the lower part of the 
vessel, whilst the hydrogen is 
evolved from the negative pole. 
After a short time, some black 
powder appears at the negative 
pole, but as the saturation of the 
acid progresses, sponge succeeds the black deposit, and 
sand succeeds sponge ; when, if the solution is for electro- 
metallurgy, the process may be stopped, for we may be 
perfectly sure, considering the large size of our positive 
pole as opposed to the negative, that the solution is suffi- 
ciently strong. 

Sometimes we vary the arrangement by using a diaphragm 
in the decomposition trough, placing the acid and positive 
pole on the one side, and on the other, with our negative pole, 




168 COMPOUNDS OF OXYDE8 WITH ALKALIES. 

some acid to render the fluid a conductor. The cut tumbler 
(figured No, 11.) answers well for these purposes. Occasion- 
ally, instead of an acid, we substitute an element dissolved 
in the water, as iodine, chlorine, bromine, and, occasionally, 
we employ a neutral salt, the acid of which unites with the 
metal, whilst the alkali is transferred over to the negative 
side. Wherever we can use an element or an acid dissolved 
in water, it is to be preferred to a neutral salt, as in my 
battery I have found a difficulty in causing the alkali to 
travel. 

The manufacture of salts by the voltaic fluid is generally 
more expensive than the processes usually adopted, and is, 
therefore, to be avoided for large commercial operations, 
especially where the metal is but of little value ; yet when we 
desire a very pure salt, a salt of a very valuable metal, or a 
salt difficult to form by the ordinary processes, then does the 
galvanic battery come into play, and, under these circum- 
stances, economy, facility, excellence, and despatch, are in- 
sured by the use of this wonderful engine, and in very many 
cases it has been found to be a really useful process. 

The solution of oxydes in alkalies is to be performed in 
the same way as the corresponding solution in acids : thus it 
may be effected by simply digesting the metal in the alkali 
— a process, however, which should always be discarded in 
practice from its slow and tedious character. These solu- 
tions may be formed by adding the oxydes recently precipi- 
tated to the alkalies; or, lastly, they may be very conveniently 
produced by making the metal the positive pole in the alkali, 
connecting it with a galvanic battery. The second process 
is generally to be preferred, but the latter will frequently be 
found convenient. 

The compounds of the oxydes of metal with salts are 
generally made by digesting them in a solution of the salt, 
or by making the metal the positive pole in their solution. 
The compounds of oxydes of metals with bitartratc of potash 



METALLO CYANIDES. 169 

and muriate of ammonia are familiar examples of this class 
of compounds. . - 

Allied to this last division of metallic compounds is a pecu- 
liar class, in which the metal, in combination with the bicar- 
buret of nitrogen, or cyanogen, forms an acid which, when 
uniting with an alkali, produces a true salt. The union of 
iron, cyanogen, and potassium, has been the longest known 
under the name of ferrocyanuret of potassium. Some phi- 
losophers, indeed, consider this salt as a double cyanuret of 
iron and potassium $ but probably the iron and cyanogen form 
a distinct proximate element, analogous in the general pro- 
perties with cyanogen, which again is perfectly analogous to 
the primitive elements, chlorine, iodine, or bromine. 

Almost any other metal may be substituted for iron, and 
an analogous compound will be formed. Thus, with silver 
an argento-cyanide, with gold an auro-cyanide, with nickel 
a nickelo-cyanide, may be made. The electro-chemical 
decomposition of all these substances is peculiar, for under 
different circumstances different results may be obtained. If 
placed on the positive side of a diaphragm apparatus, potash 
will be carried over to the negative pole, where hydrogen is 
also evolved ; Avhilst at the positive oxygen is absorbed, and 
a peculiar compound is left which presently decomposes into 
a cyanuret of the metal contained in the liquid. To take, as 
an example, the decomposition of the zinco-cyanuret of pot- 
assium, a solution placed at the positive side of a diaphragm 
apparatus has the potash carried over to the negative pole, 
while a compound, perhaps zinco-cyanogen, is left at the 
positive electrode, which speedily resolves itself into the 
cyanuret of zinc. The electro-chemical decomposition of 
ferrocyanate of potash is the same as that of the above 
metals. 

The formation of the ferro-sesquicyanuret of potassium 
has been alluded to in treating of electro-chemical decompo- 
sitions ; but Sir John Herschel having lately brought it into 

9* 




170 METALLO-SESQUICYANIDES. 

use by one of the most elegant and refined chemical processes 
in the whole range of photography, a more detailed account 
is here added. The solution of the yellow salt, which may 
be either completely or nearly saturated, is placed in a large 
porous tube, and into this is inserted as large a positive pla- 
tinum pole as possible. I generally use all the odds-and-ends 

of platinum I can collect, and _. „„ 

f , t . , Fig. 30. 

string them together with a 

platinum wire, the object being 
to bring the pole in contact 
with as much fluid as possible. 
The porous tube is placed in a 
jar containing plain water and 
a large copper negative, elec- 
trode, when on the platinum 
being connected with the silver of a compound-battery of not 
less than four cells, and the copper with the zinc, half an equi- 
valent of potash is carried over to the outer vessel, and hydro- 
gen is evolved, whilst oxygen is absorbed at the platinum side, 
and ferrocyanogen is apparently liberated, which, combining 
with the yellow salt, forms ferro-sesquicyanuret of potas- 
sium. Whether other analogous metallo-sesquicyanurets 
may be formed in the same way I have not been able satis- 
factorily to determine; the great difficulty being the uncer- 
tainty attached to the formation of a hitherto undiscovered 
salt, for we might make it and still be ignorant of the fact. 

When the metallo-cyanide is placed on the negative side 
of a diaphragm apparatus the metal itself is reduced ; thus, 
in one case we actually make the metal pass to the positive 
platinum electrode, in the other to the negative platinum 
electrode. 

When the yellow ferrocyanate of potash is galvanised in a 
porous ceil, one part becomes the red prussiate, the other re- 
mains as the yellow prussiate. If a piece of platinum be in- 
serted into each side, the yellow salt becomes positive to the 
red salt, an arrangement which I believe to be analogous to 



THE FORMATION OF METALLO-CYANII>ES. 



171 




the arrangement of the cells of Fig. 31. 

the electric eel, with the sub- 
stitution of arterial blood for the 
prussiates of potash. 

When the metallo-cyanide is 
simply galvanized between pla- 
tinum electrodes, the metal is 
reduced, and, as the result 
varies with different metals, we 
shall enter into these circumstances when treating of each 
respectively, confining our attention, however, to such facts- 
as more especially relate to the electro-metallurgist. 

When the metallo-cyanide is galvanized, the positive pole 
being the same as the metal in the cyanide, the metal, in 
most cases, is reduced from the salt, and its place supplied 
from the solution of the positive pole ; in some cases, how- 
ever, the metal is not reduced, but a salt is formed with 
the metallo-cyanide and the metal dissolved, the potash being 
transferred to the positive pole. 

Such is a rough sketch of the general properties of the 
metallo-cyanides. Wc have next to consider the mode of 
preparing this important set of salts, and numerous are the 
methods by which they may be obtained. They are formed 
most easily and usually by boiling the oxide of the metal 
with the cyanide of potassium ; but they may also be pro- 
cured by adding a solution of the cyanide of potassium to a 
solution of a salt of the desired metal, but in this case a 
foreign salt always contaminates the solution. One of the 
best processes for making metallo-cyanides is to arrange the 
metal as the positive pole in the solution of cyanuret of 
potassium. They may even be made by simply placing the 
metal itself in the solution of the cyanuret of potassium, 
when it will slowly dissolve in this truly remarkable salt ; 
even gold and palladium are readily taken up in this manner, 
especially at that part of the solution in contact with the 



172 CYANIDE OF POTASSIUM. 

air, which contact seems to favour the action — perhaps by 
causing a galvanic current, and thereby materially assisting 
the solution of the metal. Some metallo- cyanides may be 
even formed by boiling the oxyde of the metal with ferro- 
cyanate of potash, but it is not a very good process. Metallo- 
cyanides may also be formed by heating together potash, 
dry animal matter, and the metal ; when the animal matter 
affords carbon and nitrogen to form the cyanogen, which 
then lays hold of the potash and metal to form the metallo- 
cyanide. This process, with slight modifications, is generally 
adopted in the arts to form ferrocyanate of potash, which is 
used upon a most extensive scale. Whether the same 
process may be adopted for other metals, I am unable to 
state from direct experience ; but, in all probability, many 
other metallo-cyanides of potassium or sodium, might be 
made in the same manner. 

When metallo-cyanides are subjected to the voltaic force, 
curiously enough they appear, in many instances, to form a 
positive pole and take oxygen ; thus, if we use a solution of 
auro-cyanide of potassium with a gold pole, more gold is 
reduced at the negative pole than that which is dissolved at 
the positive. At different times I suppose that I must have 
received nearly a dozen letters from experimenters, who, 
noting this fact, and being ignorant of its cause, thought that 
they had actually found out a process for making gold. 

The cyanide of potassium, so often alluded to while treating 
of the metallo-cyanides, may be formed in several ways. It 
may be obtained by heating to a dull redness, the yellow 
ferrocyanate of potash in a covered iron vessel, filtering and 
rapidly evaporating it. The objection to this method, how- 
ever, is, that without great care, the whole of the ferro 
cyanate is not decomposed, a circumstance which much 
reduces its value for electro-metallurgy. By boiling, how- 
ever, the ignited residue with spirits of wine, this difficulty 
is said to be overcome, as the ferrocyanate is absolutely 



CYANURET OF POTASSIUM. 173 

insoluble in that menstruum, while the cyanuret at that heat 
freely dissolves, and is as easily redeposited on cooling. 

There is, however, a much better process by which this 
salt may be formed, namely, by simply transmitting hydro- 
cyanic acid through potassium. Although the modes of 
making this acid are very numerous, there is but one which 
is likely to be employed on a very large scale, and that is its 
formation from the yellow ferrocyanate by means of sulphuric 
acid. This process is performed as follows : any given 
weight of the yellow salt is taken and dissolved in about five 
times its weight of water; this is placed in a retort, or some 
such analogous vessel, to which is then added a quantity of 
strong sulphuric acid, twice the weight of the salt, and 
diluted with three or four times its quantity of water. A 
pipe is carried from the neck of the retort to the receiving 
bottle, which should be kept as cool as possible. For small 
operations those invaluable vessels, Florence flasks, answer 
well : a bent tube being connected at one end to its mouth, 
the other passing into the second vessel ; heat should be 
cautiously applied by means of an Argand lamp, a little 
vessel of sand being placed under the flask, which helps the 
acid to decompose the salt. Prussic acid is then generated 
and passes through the tube to the recipient vessel, which is 
to be charged with liquor potassos. When the potash is 
saturated the operation is completed. The Germans recom- 
mend a strong alcoholic solution of potassa to be used in 
the second vessel, for in this case, the hydrocyanic or prussic 
ac i# d combines with the potassa, forming a hydrocyanate of 
potassa, or, the water being abstracted, the cyanuret of 
potassium, which spontaneously precipitates on the saturation 
of the fluid, the cyanuret being insoluble in strong alcohol. 
The ferrocyanate of potash may be considered as containing 
3 equivalents of hydrocyanic acid, 2 of potash, and 1 of iron ; 
but, unfortunately, we can only obtain half the acid from the 
salt owing to the formation of a compound during its decom- 



174 PREPARATION OF PRUSSIC ACID. 

position which resists the action of the acid. The decom- 
position of this salt taking 2 equivalents or 426 grains to 
avoid fractions, would afford 3 equivalents or 81 grains of 
hydrocyanic, or prussic acid, capable of forming 198 grains" 
of cyanuret of potassium, w T hilst in the retort there would 
remain 384 grains or 3 equivalents of bi-sulphate of potash, 
and 1 equivalent or 174 grains of a peculiar compound, said 
to contain 3 equivalents of cyanogen, 1 of potassium, and 1 
of iron. (Pereira.) It is manifest that, but for this latter 
compound, we might double the quantity of hydrocyanic acid 
from the yellow salt. The decomposition just described is 
the one usually received ; but too much reliance must not be 
placed on its accuracy, for the analysis of the several com- 
pounds is too difficult for the results to be fully admitted. 
The residue left in the retort speedily turns to one of the 
blues, identical with, or allied to, Prussian blue. This is at 
best a disagreeable process to conduct, for the hydrocyanic 
acid formed adheres so strongly to the glass, that instead of 
being freely given off, bubbles are evolved suddenly with 
such explosive violence as occasionally to crack the vessel. 
This may be remedied as far as is possible by the insertion of 
plenty of waste pieces of platinum — if platinized so much 
the better, as that facilitates the escape of the gas. The 
heat should be applied to every part of the vessel, and the 
flame should not be allowed to play upon one single part 
alone. Large commercial operations are performed in green 
glass or stone-ware retorts. 

Now for one word of advice to the tyro. Remember that 
you are working with prussic acid, therefore, never conduct 
the process in a room, tho. fumes being quite as poisonous as 
the solution of the acid itself; moreover, have always a 
bottle of ammonia, or chlorine, by your side, that should 
you have chanced to inhale more than is pleasant, it will be 
instantly at hand to counteract any bad effects. It is stated 
by Pereira, that a little sulphuric acid or hydroferrocyanic 



PREPARATION OF PRUSSIC ACID. 175 

acid passes to the outer vessel, but probably the amount 
would be of no consequence for electro-metallurgy, other- 
wise, it might be as well to use a Woulfe's apparatus, and 
discard the salt formed in the first vessel. To the large 
manufacturer it may be worth considering whether some 
other metallo-cyanuret, formed in a similar manner to the 
ferrocyanuret, might not be more advantageously employed, 
because the residue of the process last-described contains 
a large quantity of cyanogen which the acid is unable to set 
free. 

There are other modes of procuring prussic acid, besides 
the one which has been so tediously described ; but these 
are found to be more expensive. The only one which I 
shall now notice is the process by which it is obtained from 
bicyanide of mercury. The bicyanide of mercury itself is 
formed when peroxyde of mercury is digested with Prussian 
blue, the peroxyde of mercury abstracting the whole of the 
cyanogen from the blue, and leaving the oxydes of iron at 
the bottom of the vessel. The solution may be evaporated 
to dryness, and one part of the salt dissolved in six of water ; 
one part of muriatic acid, sp. gr. 1 # 15, is then added, and the 
solution distilled, when the whole of the hydrocyanic acid 
passes over, and by being conducted into a solution of po- 
tassa, as in the former process, forms cyanuret of potassium. 
This process, though easier than the first described, is rather 
given as a resource under peculiar circumstances than as one 
to be adopted by the large manufacturer. The expense is 
the only objection, but in a small quantity this cannot be a 
consideration. 

In giving this very rough outline of the general mode of 
forming salts the minutiae necessary for chemical work have 
altogether been avoided ; and those parts alone are entered 
upon, which are more immediately necessary for the electro- 
metallurgist to know and practise for himself. This will 
account for the long description of the cyanuret of potassium, 



170 REDUCTION OF METALLIC COMPOUNDS. 

whilst the preparation of the equally important and even 
more used acids, the sulphuric, muriatic, &c., commonly 
found in commerce, are altogether neglected. 

In using solutions of cyanide of potassium, the workman 
should not immerse his arms into them, otherwise it occa- 
sionally happens that the solution produces very troublesome 
eruptions over the skin. 

(169.) Having now described the kind of compounds ne- 
cessary to be employed for the reduction of the metals, and 
their general preparation, and having already treated of the 
laws regulating the reduction of the metals in various states, 
the substances on w T hich they may be reduced, the various 
apparatus in which the processes may be conducted, and, 
moreover, described the various forms of galvanic batteries, 
their properties and manipulations, we are, at length, in a 
condition to consider the precise manner in which each re- 
spective metal may be reduced from its soluble compounds. 

Platinum is the first metal of which we have to consider 
the reduction. There are not many compounds of this 
metal ; the principal being the chloride, the sulphate, and 
the compounds of chloride of platinum with alkalies. The 
chloride of platinum is formed by digesting platinum in 
nitro-muriatic acid, consisting of one part of strong nitric to 
two of muriatic acid. If evaporated to dryness at a moderate 
heat, it forms the chloride of platinum. This salt is a most 
ready conductor of the galvanic fluid, and, therefore, might 
be employed with great advantage, were it cheap enough, 
for a Daniell's battery, instead of sulphate of copper. When 
we desire to obtain the black powder of platinum, this is the 
salt to be selected ; if acid, it requires great skill to obtain 
any other deposit from it. To obtain the black deposit, the 
zinc single-cell apparatus is generally to be preferred. The 
same deposit may also be obtained by the compound battery 
decomposition apparatus, by using five or six cells of the 
battery, charged with the usual strength of acid, and by 



REDUCTION OF PLATINUM. 177 

using a large positive platinum pole in the trough. Un- 
fortunately, the oxygen has always to be evolved on the 
positive pole, as the platinum does not dissolve, except to a 
very trifling amount, and fresh chloride of platinum must 
continually be added to maintain the strength of the metallic 
solution. This applies to all salts of platinum, as in no case 
is the positive pole acted upon sufficiently to supply the 
place of the metal reduced from the fluid. To obtain the 
reguline deposit of platinum from this solution, we must of 
course overcome resistances at all points of the circuit ; we 
must begin by employing a very small battery, feebly charged, 
and use a fine positive wire in the trough, combined with a 
very strong solution of the chloride of platinum. A com- 
pound odds-and-ends' battery is well adapted to obtain the 
reguline deposit ; the little glasses, of which the battery 
figured below is composed, need not contain more than an 
ounce of fluid, and four arranged as a series will be amply 
sufficient. 

At the bottom of each glass a little mercury is placed, 
containing a piece of zinc ; a piece of silver wire, either 
amalgamated or coated with some non-conducting substance, 
except at the end, is immersed in the mercury, and passes 
to a small piece of platinized silver in the next vessel ; the 

Fig. 32. 



first piece of silver and the last zinc of the series being at- 
tached to a binding-screw, a mercury cup, for the convenience 
of making metallic connections. In the battery figured, the 
ends are left free. The batteries are charged with dilute 
sulphuric acid, and a fine platinum wire is connected with 
the extreme silver of the battery, and the object to receive 



178 CHLORIDE OF PLATINUM. 

the reduced platinum with the terminal zinc. This solution 
of platinum will bear but a very feeble current when we 
desire the reguline deposit. Oxygen and chlorine are 
evolved abundantly from the positive platinum wire, which 
must not be immersed more than half an inch in the solution, 
and frequently the insertion of one-eighth or even one-six- 
teenth of an inch will amply suffice. If the solution of the 
chloride of platinum be strong, the fumes of the chlorine 
will, at length, fill the whole room in which the operation is 
conducted. 

Chloride of platinum forms double salts with several al- 
kalies. The ammonio-muriate and potassio-chloride are very 
insoluble, but the sodio-chloride of platinum, or, perhaps, 
more correctly, the platino-chloride of soda, is very soluble 
in water. This forms an excellent compound, and perhaps 
the best for the reduction of the metal in the reguline state, 
the mode of proceeding being precisely similar to that of the 
last^described salt. In fact this is, perhaps, the best salt for 
these purposes ; and as scarcely any metal reduces the pla- 
tinum spontaneously from the solution, they may be indif- 
ferently employed as a negative pole in it. 

With the electro- chemical decomposition of the sulphate 
of platinum, I am practically unacquainted ; but it is said to 
form a soluble salt. 

If hydriodate of potash be added to a solution of chloride 
of platinum, a precipitation ensues, which is soluble in excess 
of the precipitate. It forms a very dark-coloured solution 
from the presence of iodine ; to counteract which, a little 
free potash is required. It is an unfavourable salt for elec- 
tro-metallurgy, especially for the reduction of reguline 
metal. 

A platino-cyanide of potassium has been described by 
some authors, but it appears a difficult salt to manufacture. 
It can neither be made by galvanism, nor by allowing the 
metal to stand in the cyanide. If chloride of platinum be 



COST OF THE REDUCTION OF PLATINUM. 179 

added to cyanide of potassium, some change takes place, but 
I have not succeeded in making any advantageous use of it 
for electro-metallurgy. 

A hyposulphite of platinum may be formed by adding the 
hyposulphite of soda, or potash, to the chloride of platinum ; 
but this, likewise, forms a very indifferent solution for 
electro-metallurgy. 

The equivalent of platinum being ninety -nine, we obtain 
three times more in weight for our equivalent of power, than 
we should of copper, or three times more than the zinc 
dissolved in each cell of the battery ; but inasmuch as we 
know no method of dissolving reguline platinum at the 
positive pole, at least to any useful amount, we cannot 
employ a single battery, but require a series of three or 
four to effect that object. If we apply our equation to 
ascertain the cost of reducing platinum, we find that, as 
platinum in solution is worth about 201. per lb., the value 
of the power to be added to this would barely exceed 1 Id. ; 
but if the single cell could be adopted advantageously, the 
galvanic power sufficient to effect that object would not 
exceed 4d. This aspect of affairs is so exceedingly pro- 
mising that, doubtless, some manufacturer of platinum will 
enter into the galvanic process on a large scale to ascertain 
whether electro-metallurgy might not triumph over the 
Woolastonian method of working in this metal. The one 
mode, we have seen, requires a battery of almost nominal 
value, the other apparatus is of the most complicated and 
expensive nature ; so that by ascertaining the labour re- 
quired for each respective process, the relative time occupied 
by them, and the quality of the metal reduced being once 
learnt on the large scale, the question would be satisfactorily 
determined. 

(170.) Gold is rendered solvent by combination with se ■ 
veral substances, and its chloride, bromide, iodide, cyanide, 
and other compounds, all merit separate attention. 



180 REDUCTION OF GOLD. 

The chloride of gold may be formed in various ways ; by 
passing a stream of chlorine through water containing gold 
in that fine state of division termed by assayers brown gold. 
For obtaining a solution of this salt, however, such a method 
is but seldom adopted, as the metal is more commonly sub- 
jected to the solvent powers of aqua regia — a composition of 
one part nitric to two muriatic acids. The gold is placed in 
three or four times its weight of this acid, and a moderate 
heat is applied to favour the action. In this case the nitric 
acid being a highly oxygenated compound, and the muriatic 
containing hydrogen, mutually re-act on each other. Nitrous 
gas is evolved, water is formed, and chlorine set free, which 
then combines with the gold to form the chloride. By this 
mode of proceeding the compound is always acid, which is 
best removed by very carefully evaporating it, when, on 
cooling, crystals will be deposited. If the operator conducts 
his process at too great a heat, he will find that a part, or 
the whole, of the gold will be deposited in the metallic state, 
and he will be compelled to re-dissolve it. Having avoided 
this difficulty, and obtained a chloride of the metal, he will 
find it to be a very soluble salt and an excellent conductor. 
This salt may be reduced by the single-cell process, which, 
however, for gold should always be discarded, or by the bat- 
tery apparatus. In either case the hydrogen appears to have 
a great tendency to be evolved, and, therefore, the deposit of 
black powder is easily accomplished. For its reduction in 
the bright reguline state we must increase resistances. By 
using a very fine platinum pole, which affords the greatest 
resistance to the voltaic current, I have worked a solution of 
this salt quite colourless, and still obtained a reguline de- 
posit. Some better salts are now known, however, for ob- 
taining this object more readily. If the battery apparatus be 
employed, then we may use a series of three or more bat- 
teries, with a fine platinum wire. If we use a gold positive 
pole in this solution, a little is dissolved ; but it affords 



BROMIDE OF GOLD. 181 

nearly as violent a resistance to the passage of the voltaic 
current as platinum, the oxygen seeming rather to prefer to 
be evolved than to combine with the metal. This solution 
of gold is decomposed by nearly all metals, and is, therefore, 
objectionable on that account ; carbon and platinum alone 
having no effect on it. 

The bromide of gold is readily prepared by adding a little 
bromide to the brown gold of the assay ers, and allowing it 
to remain some time under water, or assisting its action by 
a gentle heat. It forms a salt of a lovely bright crimson 
colour, but in its general properties is precisely similar to 
the chloride, except, perhaps, that a gold positive pole is 
rather more quickly acted upon in it. 

Chloride of gold is soluble in aether, and in this state has 
long been used for gilding penknives, and other steel articles, 
by simple immersion. It may be used, but possesses no 
peculiar advantages for electro-metallurgy. Copper and 
silver rapidly reduce the metal from this solution. I have 
endeavoured to dissolve the chloride in naphtha, oil of 
turpentine, essential oils, and other fluids, thinking that by 
these menstrua its conducting power might be lessened, 
but, unfortunately, the gold is slowly reduced simply from 
contact with these substances. 

The hyposulphite of gold may be formed by adding the 
hyposulphite of soda or potassa to the chloride of gold. The 
solution, though not decomposed by copper or silver, does not 
answer well, as the reduced gold is apt to peel off from the 
object, and it seems as if some other substance was reduced 
conjointly with it. Gold will dissolve when made the posi- 
tive pole in this solution. 

Chloride of gold forms double salts with certain alkalies, 
especially soda and potash. They are made by simply adding 
the alkali to the metallic salt. These compounds might be 
used for electro-metallurgy, as they are not very readily 
decomposed by silver or copper, which may, therefore, be 



182 AURO-CYANIDE OF POTASSIUM. 

used as negative poles. These compounds, however, are 
very inferior to the auro-cyanuret of potassium, and the 
gold reduced from them has frequently the appearance of 
the brown gold of the assay ers. Sometimes magnesia or 
lime may be added to a solution of the chloride of gold with 
advantage. 

If a solution of iodide of potassium be added to a solution 
of gold, a precipitate of iodide of gold takes place, soluble in 
excess of the precipitate. It requires the addition of free 
potash to combine with any iodide that may chance to be set 
free by the acid in the chloride of gold. A gold positive 
pole is slightly dissolved in this solution, but it has the dis- 
advantage of yielding up its metal to silver by elective affinity, 
or else it might, perhaps, be employed, though it is by no 
means the best solution for this purpose. 

The sulphocyanide of gold is insoluble in water, but dis- 
solves pretty freely in sulphocyanide of potassium.* It has 
the advantage of not being decomposed by silver or copper. 
A plate of gold dissolves with moderate rapidity when ar- 
ranged as a positive pole in the liquid. It may be decom- 
posed in all the various ways that have been so frequently 
alluded to. 

We have now to treat of the most important salt of gold 
for electro -metallurgy, the auro-cyanide of potassium. It was 
first employed by Elkington, whose discoveries we have fully 
considered in our history of electro-metallurgy. It is a salt 
somewhat analogous to the ferrocyanate of potash, and is 
easily prepared in a variety of ways. It may be made by 
simply placing a piece of pure gold in a solution of cyanuret 
of potassium, but this process requires some little time. It 
may be formed by arranging a piece of pure gold as the posi- 

* The sulphocyanide of potassium is a troublesome salt to prepare ; 
but Mr. Low, the patentee of the celebrated Prince's or Naphtha Gas, 
informs me that large quantities are thrown away in the refuse of the gas 
works. 



AURO-CYANIDE OF POTASSIUM. 183 

tive pole in a solution of cyanuret of potassium, using, at 
the same time, a small negative pole. It may be also formed, 
and this is the process that many prefer in the large way, by 
boiling the oxyde of gold for half an hour in a solution of 
cyanuret of potassium ; the fluid may then be poured off, and 
is ready for use, whilst the remaining oxyde of gold is to be 
carefully preserved. Of these three processes, to the second 
I should unhesitatingly give the preference ; for, by using a 
strong battery, a large quantity may be made in a few minutes, 
and it only requires the metal itself, and not the oxyde, in 
the production of which alone more trouble and time is in- 
curred than is consumed in the entire manufacture of the salt 
by galvanism. The galvanic process of making salts has been 
already so fully described that no further detail is here re- 
quired, only remembering to have a strong battery, a large 
positive, and a small negative pole. There are still other 
modes by which this salt may be made ; it is, for instance, 
produced by simply adding the soluble salts of gold as the 
chloride to the solution of the cyanuret of potassium, or by 
digesting insoluble compounds of gold, as the sulphuret, in 
the same solution. It may also be formed by digesting the 
oxyde of gold in a solution of ferrocyanate of potash, and in 
this case the presence of a little of the latter salt is not very 
material, but on the whole we had better, perhaps, employ 
the pure metallic salt. 

The auro-cyanide of potassium having been formed is at 
once ready for the electro-metallurgist, and it is quite a 
matter of indifference whether it contains a little free potash, 
or a little cyanuret of potassium. The solution may be of 
any strength ; the stronger, however, is to be preferred, as 
this salt is by far the best adapted for reguline metal. The 
metal may be reduced from it by the single-cell process, for 
which a large zinc plate would be required. However, no 
one should ever think of employing this process, as by its 
means we should reduce our gold from the solution, and our 



184 AURO-CYANIBE OF POTASSIUM. 

cyanuret of potassium would be wasted. Of the battery 
processes, the compound battery, with a platinum positive 
pole, may be employed, but, unless under. very peculiar cir- 
cumstances, it is better discarded. The battery-process with 
a gold positive pole is, therefore, our resource for this salt. 
As a general rule the gold positive pole should be about the 
size of the negative pole, or that in which the reduced gold 
is being deposited. A single battery will in general suffice, 
the gold being attached to the platinized, silver, and the 
object to receive the deposit to the zinc. A very small 
battery will be required, a platinized silver wire for small 
objects being almost sufficient. I have even used a battery 
formed with a glass tube drawn to a point, with a fine 
platinum wire melted into the glass, so that a little piece is 
left inside, and the rest on the outer part of the tube ; 
some mercury with fragments of zinc is placed in the 
vessel sufficientlv high to cover the wire : the tube is filled 
with dilute sulphuric acid : and, last of all, the apparatus is 
completed by the insertion of a second platinized silver 
wire. 

The process, when a gold positive pole is employed, is 
materially influenced by the quantity of free cyanuret of 
potassium in the solution, as a deficiency in that salt causes 
the action to take place very slowly, whilst an abundance so 
much increases the action, by dissolving the positive gold 
pole with great rapidity, that the deposition is very speedily 
effected. Any other form of battery may be employed in- 
stead of the small one mentioned, taking care to adjust it ac- 
cording to the three laws already detailed. One of the little 
batteries figured above for the reduction of platinum may be 
very conveniently used. 

It is a high penal offence to tamper with the coinage, 
and only a few years ago the offence was punished with 
death. Under these circumstances, the electro-metallurgist 
should not be invited to try experiments with his coins, 






REDUCTION OF PALLADIUM. 185 

which, always being at hand, are very tempting to the mani- 
pulator. 

The reduction of gold by galvanism is accomplished at a 
low rate, for as the equivalent of gold is very high *, and its 
value great, we find the galvanic process a most advantageous 
mode of proceeding. We obtain for one equivalent of power, 
costing 2V of sl penny, 200 grains of pure gold, worth about 
21. ; and, therefore, lib. avoirdupois of gold would be re- 
duced for less than 2c/., and the gold so reduced would be 
worth nearly 70/. The power from the magneto-electric 
machine is also well adapted for the deposition of gold. 

(171.) Palladium is a noble metal, but has the singular 
defect of being brittle when hot. It would be extremely 
valuable were there to be found any great consumption for 
it, but the supply happens to exceed the demand ; and, there- 
fore, it is moderately cheap, considering that its usual mode 
of manufacture is similar to that in use for platinum. There 
are various salts from which it may be reduced : its nitrate, 
its ammonio-chloride, and its palladio-cyanide, are the prin- 
cipal I shall notice. 

The nitrate of palladium is formed by digesting the metal 
in nitric acid, and the process is facilitated by the addition 
of a few drops of muriatic acid. It is a ready conductor, 
and in its general electro-metallurgical characters is precisely 
similar to the chloride of gold or platinum. It is better 
adapted for the reduction of the black powder than the 
reguline metal. The palladium is reduced from this solution 
by many metals, and perhaps only carbon, gold, platinum, 
and palladium can be used as a negative pole. 

The ammonio-muriate of palladium is very soluble in am- 
monia, and is the best salt for obtaining the reduction of 



* I have assumed the usual chemical equivalent of gold, 200, to be its 
voltaic equivalent, but have no authority for that assumption, as Faraday, 
the only authority on this subject, has not determined it 

10 



186 REDUCTION OF IRIDIUM AND RHODIUM. 

palladium in the reguline state. The compound battery ap- 
paratus is to be preferred for this purpose, two or three cells 
being required. In the decomposition trough, the positive 
pole should consist of a very fine platinum wire, which should 
be immersed only to a moderate extent in the fluid. This 
salt is not readily decomposed by other metals, and on that 
account nearly all may be used as a negative pole to receive 
the palladium. During the decomposition the positive pole 
has a bright yellow powder deposited upon it, giving it the 
appearance of being converted into gold. 

The iodide of palladium is formed by adding iodine of potas- 
sium to a solution of palladium. It may be dissolved in ex- 
cess of the precipitant. It is by no means a valuable salt 
for electro-metallurgy. 

The palladio-cyanide of potassium may be formed by simply 
immersing palladium in a solution of cyanide of potassium, 
when it will be gradually dissolved ; or it may be made by 
galvanism, or even by boiling the oxyde in the cyanuret of 
potassium. It may be employed with a palladium positive 
pole, or with a platinum positive pole, but the former is to 
be preferred. 

The reduction of palladium is accomplished at a low cost, 
as far as the materials are concerned, for palladium being a 
valuable metal and a high equivalent, requires but a small 
amount as the cost of galvanic power to be added to the 
value of its solution. 

(172.) Iridium has but few soluble salts ; of these however 
the chloride may be mentioned. The black deposit of irid- 
ium is easily reduced from its solution, and is very frequently 
found on the platinized silver of commerce, which is, perhaps, 
the only fact concerning the metal worth recording. I have 
reduced this metal in the bright reguline state, but only on 
a ^mall scale. 

(173.) Rhodium forms soluble salts, of which the only one 
1 have subjected to the voltaic fluid is the sodio-muriate. 



REDUCTION OF OSMIUM AND SILVER. 187 

It was decomposed with a compound battery of ten cells 
with platinum electrodes, the positive consisting of a very- 
slender wire, — at the negative a deposit of rhodium took 
place. It was of a w T hitish colour, and might be stripped off 
from the platinum in small pieces, but was very brittle. 
A black powder was deposited by a more powerful voltaic 
current. 

(174.) Osmium has a soluble oxyde, but subjected to the 
voltaic fluid between platinum poles it did not yield reguline 
metal, but a black deposit, which appeared to be the metal in 
a lower state of oxydation than the volatile soluble oxyde, 
and not the black powdery metallic deposit. 

(175.) Silver, on account of its universal importance, 
demands our most serious attention. The nitrate, sulphate, 
acetate, hypo-sulphite, ammoniuret, and several others, must 
be separately considered, though the argento-cyanide of po- 
tassium is most decidedly entitled to the preference. 

As a solution, from which the silver- is to be reduced, the 
nitrate is for all purposes the most unfavourable. When 
this salt is used, the hydrogen has a great tendency to be 
evolved from it, and therefore a relatively feeble current 
must be employed. The decomposition cell may contain a 
positive pole of platinum, or even of silver, as the latter 
will, by being dissolved, alw r ays maintain the same state of 
saturation of the fluid. When we use a positive pole of 
silver, there is a risk of materially increasing the quantity of 
electricity, and therefore only a silver wire should be 
employed; and then the distance at which the operator 
places them in the fluid, will accurately regulate the amount 
of current. The negative pole to be placed in this solution 
for the purpose of receiving the precipitated metal, may 
consist of either gold, platinum, charcoal, or silver ; but the 
other metals are not at all fit for the purpose, owing to the 
energy with which they decompose the solution. The 
strength of the solution of this salt may be from 10 to 420 



188 SALTS OF SILVER. 

grains to the ounce of water, taking care that the electricity 
is regulated in its quantity, according to the strength of 
the solution, in the manner already directed. 

The sulphate of silver is easily formed by adding sulphuric 
acid to a saturated solution of nitrate of silver, as, by its be- 
ing far less soluble than the nitrate, it is very quickly de- 
posited. The supernatant liquor is to be poured off and well 
washed with a little distilled water, when it is ready for the 
operator. It is not so easily decomposed as the nitrate, nor 
so ready a conductor, but it is a very inferior salt for electro- 
metallurgy, as the silver, under the most favourable circum- 
stances, is very brittle. 

The acetate of silver is formed in an analogous manner to 
the sulphate, and in its conducting power and facility of de- 
composition much resembles it. In both these cases, a silver 
positive pole may be employed in the decomposition appa- 
ratus, and a single battery of small power for the source of 
electricity. 

The hypo-sulphite of silver may be readily made, by 
adding any hypo- sulphite, such as that of potash, to the 
nitrate, chloride, or any other salt of this metal. There 
appears to be a strong attraction between silver and this acid, 
as the hypo-sulphite decomposes the most insoluble salts of 
silver. The hypo-sulphites of the alkalies may be prepared 
by adding sulphurous acid to their sulphurets ; as, for 
instance, to the sulphuret of potassium or sodium. This 
salt of silver is pretty soluble, and will bear a larger quantity 
of electricity for its decomposition than the nitrate, sulphate, 
or acetate, but generally the hypo-sulphites are not well 
adapted for electro-metallurgy, and in this case the metal 
is apt to be brittle. A silver positive pole dissolves in 
this salt. 

The ammonio-nitrate and ammonio-chloride of silver are 
very soluble salts. Great care is required in the use of these 
salts ; for if the solution, by being kept for some time, be 



SALTS OF SILVER. 189 

allowed to evaporate, so as to leave dried portions adhering 
to the sides of the vessel, it can no longer be even touched 
with safety ; for a fulminating salt is thus formed, which, if 
merely touched with the finger, in order to remove it from 
the sides of the vessel, will explode with mischievous and 
awful violence. I take particular notice of this fact, as I 
nearly lost my right eye in learning it. These salts are good 
conductors, and their solutions may be used of any strength. 
They should invariably be alkaline, from excess of ammonia. 
A negative pole, suitable for the reception of the silver, may 
be made of platinum, gold, palladium, carbon, or silver itself; 
all of which are unaffected by the solution, and thus whenever 
we desire a duplicate of silver, the original should always 
consist of those metals. 

A very fair solution for the reduction of silver is the 
ammonio-carbonate. It is formed by adding carbonate of 
ammonia in large excess to nitrate of silver. Carbonic acid 
is disengaged with effervescence, and a white powder is 
deposited, which, on further excess of the ammonical salt, 
becomes soluble. It may be used with a silver positive pole, 
a mere wire sufficing, and a single battery. 

The iodide of silver produced by adding iodide of potas- 
sium to the solution of nitrate of silver, and dissolved with 
excess of the precipitant, may be employed for electro-me- 
tallurgy. It is not decomposed by copper, and may be used 
with a silver positive pole and single battery. 

The sulpho-cyanide of silver formed by adding sulpho-cy- 
anide of potassium to the nitrate of silver, and then dissolving 
the precipitate with excess of the sulpho-cyanide, may be 
employed like the iodide. A positive pole of silver dissolves 
in this solution. 

A potassio-tartrate of silver is formed by boiling oxyde 
of silver in bitartrate of potash. It is easily decomposed by 
light, and possesses no advantage for electro-metallurgy. 



190 ARGENTO-CYANIDE OF POTASSIUM. 

The spongy mass can be obtained from any of these salts, 
with the utmost readiness, by increasing the quantity of elec- 
tricity. 

In the electro-chemical decomposition of nearly all the 
above salts of silver, where the positive pole consists of the 
same metal, a black crust is very frequently observed on the 
silver, which very probably is a peroxyde of silver analogous 
to the peroxyde of lead, &c. 

We have, at last, to treat of by far the best solution of 
silver for electro-metallurgy, which is the argento-cyanide of 
potassium. This may be formed by digesting the oxyde of 
silver with ferrocyanuret of potassium, but this constitutes a 
very imperfect process. It may even be prepared by adding 
any soluble salt of silver to a solution of the cyanuret, or even 
by digesting the insoluble salts in the same solution, but in 
these cases, a new salt is formed between the radicle of the 
salt of silver, and a part of the potassium besides the part 
required for the formation of the argento-cyanuret of potas- 
sium ; thus chloride of silver and cyanuret of potassium form 
chloride of potassium and argento-cyanide of potassium. It 
is far better to prepare it by boiling a portion of the oxyde 
of silver for a few minutes in a solution of the cyanuret of 
potassium, and pouring off the supernatant liquor ; the un- 
dissolved oxyde is to be washed and carefully preserved for 
subsequent operations. The best mode, however, of prepar- 
ing this salt is, to make a large silver plate the positive pole 
in a solution of cyanuret of potassium, using, at the same 
time, a very small negative pole in connection with a strong 
battery, and continuing the process till reguline silver begins 
to be deposited at the small negative pole, when the operator 
may be perfectly well-assured that for all larger negative 
surfaces his solution is sufficiently strong : the little super- 
fluity of cyanide of potassium, by favouring the conducting 
power of the solution, facilitates the reduction of the metal. 
The argento-cyanide of potassium, if suffered to crystallize, 



ARGENTO -CYANIDE OF POTASSIUM. 



191 



forms clear, colourless crystals, and the solution should also 
be colourless. If it is at all yellow, it shows the presence 
of ferrocyanate of potash, which it sometimes contains in 
commerce. 

However formed, this salt, first used and patented by 
Elkington, is by far the best adapted for electro-metallurgy. 
It may be employed of any strength, the nearly saturated 
solution being preferable, and it should always be placed in 
a glass or stone- ware vessel. It may be reduced by the 
single-cell process, taking care to use on the positive side of 
the diaphragm apparatus a very large plate of zinc, with a 
solution containing a little muriate of ammonia, or common 
salt ; but no electrician would ever think of employing this 
apparatus for the reduction of silver, for the cyanuret of 
potassium in combination with the silver would be wasted. 
The compound battery apparatus with a platinum pole may 
be used, but should, as a general rule, be discarded, and the 
single battery apparatus invariably be employed. The posi- 
tive pole may be the same size as the negative, and should 
consist of a piece of thick silver sheet, one-third of an inch or 
more in thickness. The 
battery need not be very Fig. 33. 

large, for the conducting 
power of the metallic solu- 
tion being low, only a 
moderate quantity of elec- 
tricity passes. For small 
drawing-room operations, 
a tumbler battery with a 
glass precipitating-trough forms a most elegant instrument 
for amusement, and the largest manufacturer has only to 
increase the size of his trough, which should be glass or stone- 
ware, and regulate the size of the battery to it. The plate 
of silver must be connected with the silver of the battery, 
and the object to receive the deposit with the zinc. The 




192 REDUCTION OF SILVER. 

presence of even a large portion of ferrocyanate of potash in 
a solution of the argento-cyanide is of little consequence in 
strong solutions, but in very dilute ones the positive pole be- 
comes covered with a white deposit of ferrocyanate of silver, 
which materially retards the action. The presence of free 
cyanuret of potassium adds to the conducting power of this 
salt, and much facilitates the quickness of the deposition of 
the metal, and therefore as much should be contained in th( 
solution as can be added without causing the metal to be 
thrown down in the various states of spongy deposit. The 
metal reduced from the salt, especially if reduced with the 
utmost speed that the strength of the solution will allow, is 
as perfect in its physical properties as the best rolled metal, 
combining elasticity with softness and flexibility, and the* 
decomposition may take place to any extent. 

It was accidentally discovered that a few r drops of bi- 
sulphate of carbon confer peculiar qualities upon the silver 
solution. The metal, instead of being thrown down with 
a matted appearance, is deposited as brilliantly as though it 
were burnished. The discovery of this fact is very im- 
portant to the manufacturer, inasmuch as it saves a vast 
amount of labour in burnishing and polishing. The dis- 
covery is patented, and is now generally adopted at 
Birmingham. 

■ The magneto- electric force is well adapted for silver. I 
have been informed by Mr. Elkington, that he is con- 
structing a magneto-electric machine, which is supposed to 
have sufficient force to reduce fifty ounces of silver per 
hour. 

The reduction of silver metal is very easily performed, 
and is economical. The equivalent of the metal is 108 ; there- 
fore, for one equivalent of power, costing ^V of a penny, we 
obtain that quantity of silver ; or the reduction of lib. avoir- 
dupois of silver, worth £4 4s., would by the simple battery 
process cost less than 4c7. For further particulars of the 



EEDUCTION OF NICKEL. 193 

cost of the reduction of this metal, the student is referred to 
the equations and data given in a former chapter. 

(176.) Nickel is the last in the list of noble metals, being 
the most ignoble of that class. The nitrate of nickel, the 
sulphate of nickel, the ammonio-nitrate and sulphate of 
nickel, the nikelo-cyanide of potassium, but especially the 
chloride of nickel, require consideration. The nitrate of 
nickel is very soluble, but the metal has no great inclination 
to be precipitated, for the hydrogen appears rather to prefer 
being evolved than to reduce the metal. If the compound- 
battery process be used, the positive pole should consist of a 
fine platinum wire, and should only be immersed for a short 
distance in the solution. The sulphate of nickel is also a 
soluble salt, and the metal is reduced more readily from it 
than from the nitrate* It is best reduced by the compound- 
battery process, with a platinum positive pole, though a 
nickel positive pole may be employed. When we employ 
either the nitrate or sulphate of nickel for electro-metallurgy, 
it is preferable to use the solution as strong as possible. 
Of the compounds of these salts with the alkalies, those of 
ammonia deserve the preference, and the ammonio-nitrate 
and the ammonio-sulphate may be used for the reduction of 
this rather troublesome metal. - 

Nickel forms a compound with the cyanide of potassium 
by boiling the oxyde in a solution of that salt, which takes 
up a considerable quantity. The solid salt is of a yellow 
colour, though the solution generally is of an orange tint. 
Even in this solution, the hydrogen seems much rather to be 
evolved than to reduce the metal, and for this reason we must 
have a very feeble power in relation to the strength of the 
solution. 

The acetate of nickel is easily formed, by adding pyrolig- 
neous acid to the oxyde of nickel. It forms a green salt, and 
may be decomposed either by the compound-battery with a 
platinum pole, or even by using a nickel positive pole ; but 

10* 



194 REDUCTION OF COPPER. 

it is a bad solution for obtaining reguline metal, though the 
black powder can be obtained with ease. 

The chloride of nickel is formed by digesting the metal in 
muriatic acid. It forms a fine green-coloured salt, and a 
very excellent one for our purposes, as hydrogen in this case 
has not nearly so great a tendency to be evolved. It may 
be used with a nickel positive pole with one or two 
batteries, or with a series of two, three, or four little odds-and- 
ends' batteries, and a platinum positive pole. The nickel so 
deposited has a peculiar white brilliant lustre, looking almost 
like glass, — this deposit is so very beautiful, though brittle 
when removed from the negative pole, that its examination 
would amply repay any person taking the trouble to 
precipitate it. It is such a contrast to the nickel of the 
shops, that no person would ever suppose that there was any 
similarity of composition between the substances, still less 
identity. For practical purposes this salt is perhaps to be 
preferred to all the others which have been mentioned, and, 
next to the chloride, the sulphate is the best for the reguline 
deposit. 

Any of the above solutions will yield readily the pulveru- 
lent deposit by using a very strong galvanic current. 

Nickel possesses but a low equivalent, only 28 grains 
being deposited for one equivalent of power worth -^\ penny. 
The voltaic reduction, therefore, of an avoirdupois pound, 
worth 7*., would amount to about Is. 

(177.) Copper requires more than ordinary examination, 
because the purposes for which its reduction by voltaic elec- 
tricity has been applied are far more numerous than those 
of any other metal. Its reduction may take place from 
several of its salts, of which the sulphate, muriate, nitrate, 
and acetate, are the most worthy of attention. The sulphate 
is most commonly used, because it is the cheapest. It 
deposits thirty-two grains of pure metallic copper, for every 
hundred and twenty -five grains of the sulphate, decomposed 






REDUCTION OF COPPER FROM ITS SULPHATE. 195 

by the voltaic current, and thirty-two grains of zinc are dis- 
solved for every thirty-two grains of copper which are re- 
duced. In the use of all the salts of copper w^e must call to 
mind the function of water in voltaic arrangements to dissolve 
the newly-formed metallic salt ; and, therefore, we must take 
care never to employ solutions of the salts of copper at the 
utmost degree of saturation, but have a superfluity of that 
very important agent in our arrangements. Copper may be 
very readily reduced from a dilute neutral solution of the 
sulphate, and, in fact, from a solution of any strength, ac- 
cording to the laws given for the reduction of metals. It is 
however, a salt of rather difficult decomposition, and offers 
considerable resistance to the passage of the electric current. 
Its conducting power, and, therefore, its facility of decom- 
position, may be increased by adding acid to the solution, 
which may be either dilute sulphuric, or dilute nitric. A 
solution, made by dissolving one pound of the salt in four 
pounds of water, and by afterwards adding from one-third 
to one-half of its bulk of dilute sulphuric acid, is best 
adapted for many purposes. The dilute acid should consist 
of one part sulphuric acid to eight of water, well mixed 
together. This solution answers extremely well, when we 
have to cover non-conducting substances, to which a metallic 
or black lead covering has been given ; because the 
hydrogen, with a sufficient battery, has not such tendency to 
be evolved. 

It is very desirable that the solution of copper should be 
as pure as possible, as that which is sold generally contains 
some salts of iron. Perhaps it would be well worth the 
attention of any electro-metallurgist to make his own 
sulphate of copper, by using distilled sulphuric acid, and a 
positive pole of the best copper which he can purchase. The 
positive pole should be very large, the negative very small ; 
the acid should be diluted to the strength which he desires 



196 REDUCTION OF COPPER FROM ITS SULPHATE. 

his solution, and the whole should be connected with an 
active battery. 

A variation may be made in the fluid, by employing 
rather less dilute sulphuric acid, and at the same time adding 
a little nitric acid, by which the conducting power of the 
solution is materially increased. A solution formed by a 
saturated solution of sulphate of copper, diluted with one- 
third its bulk of dilute sulphuric acid as before, and to which 
two drachms of strong nitric acid are added, in the pint of 
fluid, forms the most unexceptionable solution for general 
purposes. The lateral growth of the copper in this solution 
takes place to a great extent, — a property which always 
enhances the value of the process. The nitric acid attacks 
the positive pole, so that the metallic solution is apt to 
become stronger. "When this takes place, the solution must 
be diluted. The positive pole is more apt to be attacked 
after the action has continued some little time, for nitrous 
acid is formed, which assists the solution. In both these 
cases, the reduction takes place with considerable rapidity. 
The effect of the acids is to diminish the resistance offered 
to the passage of the electric current, which is virtually 
equivalent to increasing the intensity ; and we find that the 
quality of the copper obtained by either of these methods is 
the same, being soft, flexible, malleable, and ductile, but not 
very elastic. To obtain these qualities in the most eminent 
degree, the voltaic power should be so regulated to the 
strength of the solution, that a little more would cause the 
evolution of a few bubbles of hydrogen. We generally re- 
quire the copper to be somewhat harder, and more elastic 
than this ; to accomplish which we slightly increase the 
strength of the solution. 

The acid solution must not be employed when the 
negative plate, or mould, to be copied consists of a more 
oxydable metal than copper ; for the acid would act upon it, 
and perhaps even entirely dissolve it. In this case, a neutral 



COPPER OF VARIOUS QUALITIES. 197 

solution must be used. If in these cases the copper is 
required to possess the qualities which I have before 
described, a series of two, three, four, or more batteries must 
be used if a strong solution be employed, by which means 
intensity is obtained, and the tendency to the evolution of 
the gas is increased. The cost would be, at the same 
time, double, treble, or quadruple that attending the 
application of one battery. A flexible state can be also 
obtained by using a dilute neutral solution, with a single 
battery, or even by employing a stronger solution kept at an 
elevated temperature. The student will now begin to 
perceive the value of the grand principle — the regulation 
of the amount of electricity to the strength of the metallic 
solution. 

We can obtain the copper of the utmost possible hardness, 
though slightly brittle, if we are desirous of employing it in 
that state, by adopting a somewhat different arrangement ; 
we employ a saturated solution of sulphate of copper, 
without any acid, a very large positive pole, and we use a 
cell of such a size that a considerable quantity of electricity 
is generated. In this case the copper will be found ex- 
tremely hard, and somewhat crystalline in its appearance. 
This state may be termed the greater crystalline, and the 
brittleness depends upon the crystals which form its structure, 
as a mechanical dissection will show : for if a piece of this 
copper be broken, a slight adhesion only will exist between 
the different particles of the copper. When we throw down 
the copper, however, in this state, it is apt sometimes to 
play curious freaks ; for the reduced metal, appearing to be 
abundant, passes to the back of the plate, causing nearly as 
much deposit behind as before. Sometimes it will pass to 
the corner, producing efflorescences apparently from a similar 
cause. 

From the preceding statement it is apparent, that it is 
quite a vulgar error to suppose that the brittleness or 



198 TIME REQUIRED FOR THE REDUCTION OF COPPER. 

flexibility, the hardness or softness of the copper, depends 
alone upon the greater or less quantity of electricity passing, 
or, in other words, upon the rapidity of the process, for a 
plate may be a fortnight in its precipitation, and yet so 
brittle as to break with the slightest touch- and again, when 
the process has been performed in two days, or even twenty- 
four hours, the metal has exhibited great flexibility. We 
may reverse these results by altering the circumstances ; 
thus, a plate may be a fortnight in the making, and by using 
a weak solution and a slight current, be yet flexible ; or it 
may be made in two days, and still brittle, by using too 
small a quantity in a very strong solution. The flexibility 
depends upon the quantity of electricity being suited to the 
facility with which the reduction of the metal from any 
solution is effected, and upon the quantity of salt contained 
in the solution ; thus, with a neutral solution of sulphate of 
copper alone, in order to obtain a flexible and soft plate, a 
small quantity of electricity must be employed, and that with 
a weak solution, if it be attached to only one cell of the 
battery ; a stronger solution may be used with a series of 
batteries with the same result. If the solution be very acid, 
a more considerable quantity of electricity of a single cell 
will pass, therefore more sulphate of copper may be employed 
with the same result, agreeably to the laws regulating the 
precipitation. 

Extreme brittleness may be produced by using a deficient 
quantity of electricity in a strong solution. In fact, the 
plate looks as if it were nothing but an agglomeration of 
bright metallic sand, the particles having no greater cohesion 
than those of common sand-stone. This state may be called 
the lesser crystalline. 

The copper may be always thrown down as a black 
powder, a spongy or sandy deposit, by employing a very 
powerful battery, or by the other general methods stated in 
the description of the laws. The sandy deposit, arising 



NITRATE OF COPPER. 199 

from too much electricity, must not be confounded with that 
from too little. They are, indeed, easily distinguished : the 
former always containing more or less traces of the darker 
spongy deposit ; while the latter possesses a metallic bril- 
liancy ; either of them are equally brittle. 

The nitrate of copper is a salt far more easily decomposed 
than the sulphate. It is an expensive salt, out of all pro- 
portion to the trouble of preparing it. In the form of 
apparatus, however, where the solution is kept at the same 
strength by the aid of a copper positive plate, the first 
expense is the only one incurred. The electro-metallurgist 
may readily prepare this salt for himself by dissolving 
metallic copper in nitric acid. The operator must be careful 
not to expose himself to the nitrous fumes which are then 
generated, as, by inhaling them, the pulse would be lowered, 
and other disagreeable consequences produced. It may be 
acidulated with nitric acid, which will increase its conducting 
power materially, so much so that scarcely any impediment 
will be offered to the current of a single pair of plates when 
a positive copper pole is employed. 

There is one objection to the use of nitrate of copper, for 
the hydrogen not only reduces the copper, but is enabled to 
decompose the nitric acid. This does not indeed occur 
when the acid remains as nitric acid to any great extent, 
bub as soon as a little of it is decomposed and nitrous acid set 
free, it is apt to form little bubbles of deutoxyde of nitrogen 
on the negative plate, which remain adherent to it, and 
finally becomes encased with copper. A plate of copper will 
sometimes be completely cellular from this cause, appearing 
like a sieve when held between the eye and the source of 
light. 

When this solution is employed, a pound of the salt may 
be dissolved in a pint and a half of water, and acidulated 
with half an ounce of strong nitric acid. From a saturated 
and acidulated solution of this salt, we can obtain a copper 



200 MURIATE OF COPPER. 

plate in the most rapid manner possible. The positive 
copper pole should be of the same size as that of the negative 
plate, and the two poles should be placed within half an inch 
of each other. A series of from four to six batteries must 
be employed at ordinary temperatures, though at high tem- 
peratures less would suffice. A plate of copper should never 
be made by the compound battery process, however, unless it 
be wanted in a great hurry, for although the copper is the 
same in quality, or even slightly superior to that obtained 
by one battery cell, yet the expense attending its precipi- 
tation is greater. 

For all the ordinary purposes for which the reduction of 
copper is required, there is no objection to the use of a 
small quantity of the nitrate in the solution, and indeed 
such should always be employed. There is no solution from 
which good copper may be obtained more readily than the 
sulphate to which a little of the nitrate has been added. 
For this reason I have mentioned the use of the nitric acid 
in the solution, when treating of the sulphate, and be it 
remembered that if the nitrate of copper is small in quantity 
relatively to that of the sulphate in any solution, the bubbles 
of deutoxyde of nitrogen, which alone prevent the universal 
adoption of that salt, never occur. 

The muriate of copper may be employed, but I do not 
know that any advantage attends its application. It is not 
so readily decomposed as the nitrate, but more readily than 
the sulphate. From my own experience it is one of the 
worst, if not the very worst solution, for the reduction of 
copper, as the metal is apt to assume a very peculiar ap- 
pearance. From this peculiar deposition of copper the 
presence of muriatic acid had better be prohibited, and, 
therefore, we should be very careful never to add it to our 
solutions of copper. In the employment of the single-cell 
apparatus muriatic acid should never for the same cause be 
employed even at the outer or zinc side, for we must re- 



AMHONIO-NITRATE OF COPPER, ETC. 201 

collect that almost all diaphragms allow a tolerably easy 
passage of the liquid from one vessel to the other. 

Other salts may be used, as the ammoniuret, acetate, and 
hypo-sulphite ; these salts offer no advantage, when copper 
or any other metal of less affinity for oxygen is used for the 
negative plate ; yet, with metals having a greater affinity for 
oxygen, they may be employed with advantage, for it is 
important that the negative metal of itself should exert no 
action upon the saline solution, otherwise the duplicate will 
be impaired. 

Acetate of copper is formed by digesting common verdigris 
in acetic acid, and evaporating the product till crystals are 
obtained. It is a salt difficult to decompose, requiring the 
intensity of several cells. It is not decomposed by iron 
whilst neutral. 

The compounds which ammonia forms with the salts of 
copper, are the ammoniuret of the oxyde, the ammonio-ni- 
trate, and ammonio-sulphate of that metal ; the reduction 
of the metal from these is attended with difficulties, and it 
is requisite that the solution be alkaline from the presence 
of free ammonia. Iron and steel do not spontaneously 
decompose these compounds, but I am afraid that this, the 
only benefit attending their application, will not compensate 
for the trouble and difficulty attendant on the process. The 
last salts require a series of batteries to effect their decom- 
position, although a positive copper pole be used. 

The oxyde of copper is very soluble in the muriate of 
ammonia, but it forms a very bad solution for the precipi- 
tation of the reguline metal, as hydrogen seems to have a 
great tendency to be evolved in it. Cupreous sponge is 
best obtained from this salt. 

We cannot employ a solution of iodide of copper in 
hydriodate of potash, for iodine is continually being set free 
if iodide of potassium be added to a soluble salt of copper. 
Repeated washings of the precipitate will not help us. 



202 CITRATE OF COPPER, ETC. 

The sulpho-cyanide of copper I have tried, but do not 
like it for electro-metallurgy. The solution in sulpho-cyanide 
of potassium does not contain much metal. A copper positive 
pole is but feebly acted upon in it. 

The cupro-cyanuret of potassium is another salt, which 
has yet to be described. It may be formed by boiling the 
oxyde in cyanuret of potassium, or by making a sheet of 
copper a positive pole in a solution of the cyanuret of 
potassium. The salt when evaporated forms small white 
crystals ; the solution is not a very ready conductor, but 
may be improved by the addition of free cyanuret of potas- 
sium. The only possible advantage it possesses for electro- 
metallurgy is its non-decomposition by iron, though very 
fair reguline metal may be reduced from it by either of 
the battery processes. 

Sulphate of copper forms a great many double salts ; thus, 
we have a sulphate of copper and potash, sulphate of copper 
and magnesia ; and there are a great variety of other double 
salts, as it forms compounds with almost all the alkalies, 
earths, and even some of the metallic oxydes. From the 
electro-chemical decomposition of these, nothing has turned 
up beneficial to the electro-metallurgist, and a great number 
of them when submitted to experiment were decomposed by 
iron. 

The compounds of oxyde of copper with vegetable acids 
offer no advantage. The citrate might be used, as it is 
soluble, and a copper pole dissolves in the liquid ; but iron 
reduces it, so that, being but an imperfect conductor, although 
otherwise an excellent solution for the reduction of copper in 
the reguline state, it is never likely to be employed. 

The tartrate of copper forms rather an insoluble salt, and 
the potassio-tartrate cannot be turned to any good account, 
from the very slight action that the copper pole undergoes 
in the solution. 

There are even many other salts of copper, as the com- 



COPPER POSITIVE POLE. 203 

pounds of the oxydes with the acids of fat, &c, but they are 
insoluble ; and there exist, moreover, a great variety of other 
salts of this metal which water does not dissolve. 

As a summary of the modes of proceeding with various 
solutions of different strengths, it is to be observed, that the 
more readily any particular salt can be decomposed, the 
stronger may be the solution ; the more difficult of decompo- 
sition, the weaker. A more concentrated solution of a salt 
requires more intensity and quantity than a weak solution, 
whilst a weaker solution may have the current of a single 
battery passed through it. These comprise the whole of the 
practical secrets for regulating the quality of the copper, 
and they have materially assisted in the discovery of the 
general laws which have been already laid down, for, in every 
case, the hydrogen is near its evolution when the texture of 
the copper is at its utmost degree of tenacity. 

It has been mentioned that rolled copper may be used as 
the positive plate of the decomposition cell, as, during the 
action of the battery, the metal is dissolved to the same extent 
as it is reduced at the negative plate. It is curious to notice 
how regularly that part of the plate which is opposite to the 
negative pole is thinned, until the whole is removed. From 
the amount of action being greater opposite to the surface 
receiving the metallic deposit, it happens that when a medal 
is allowed to remain for some time opposite a piece of copper, 
during the process, that a circular hole is formed in the posi- 
tive plate. For this reason, it is advisable so to vary the 
arrangement of the negative and positive surfaces, that every 
part of the plate of copper to be dissolved should be equally 
acted upon ; but during this process a considerable quantity 
of black matter, apparently charcoal, is left, arising from im- 
purities in the manufacture of the copper. The ordinary 
sheet copper of the shops appears a compound of copper and 
carbon, more analogous to steel than to pure copper. This 
carbon it acquires in the very curious process called polling, 



204 VARIOUS NEGATIVE POLES. 

which is performed by allowing willow sticks to be charred 
by the melted copper when the metal absorbs a certain portion 
of the charcoal. The black matter is not always attributable 
to charcoal, for it appears to a much greater extent in a 
neutral than in an acid solution ; in which case it appears 
to be partly owing to the formation of an oxyde of the metal. 
If an electrotype plate be made the positive pole of the ap- 
paratus, no remains will be left, but every particle will be 
dissolved. The piece of copper forming the positive pole of 
the trough may be partially dissolved by coating the rest 
with any varnish or substance which can resist the action of 
the fluid, a property of which hereafter we shall have more 
particularly to speak. 

The negative pole to receive the reduced copper may 
consist of a solution of sulphate of copper, plumbago, char- 
coal, gold, silver, platinum, palladium, [nickel, or copper 
itself, all of these being suitable for the reception of copper. 
All other metals are, more or less, acted upon by the solu- 
tion, though lead and its alloys may be used with the sul- 
phate, especially if it be diluted. Tin is much inferior to 
lead for the reception of this metal, as it acts more readily 
upon its salts. 

The same observations apply to the nitrate of copper, 
except that lead, tin, and their alloys, much more readily act 
upon them than upon the sulphate, and that iron does not 
quite so readily decompose this solution as it does the sul- 
phate. Almost all metals may be employed as the negative 
pole in the ammoniurets of copper, and also in the cupro- 
cyanuret of potassium, for they so feebly act upon these 
solutions as to make it scarcely worth consideration. Iron 
and even zinc produce but little change upon them. 

The copper thus reduced, assumes the form and appear- 
ance of the cast on which it is deposited. If the surface 
of the original be polished, the duplicate will be so likewise, 
and the colour will, in many cases, be slightly influenced, 



REDUCTION OF COPPER BY SINGLE-CELL PROCESS. 205 

especially where copper has been used as the original. The 
surface is not quite so brilliant, where lead, tin, and such 
metals are employed, but when black lead is applied on 
smooth surfaces, as sealing wax or white wax, the surface 
of the duplicates is perfectly bright. 

When we desire to clean the surface we can easily effect 
our object by brushing it over with charcoal and water, or 
with emery and water, which speedily removes any extra- 
neous matter from the surface. It is by no means a good 
plan ordinarily, to plunge the metal in acid and water, to 
effect this object, as it acts upon the surface and injures the 
brilliancy of the metal. 

Copper may be reduced by the single-cell process, from 
a great variety of salts by means of zinc, tin, lead or iron ; 
the first and last, however, being the only metals likely to 
be employed. The advantages and disadvantages of the 
single-cell in comparison with the battery apparatus, have 
been fully discussed in the first chapter of the second book ; 
but if there is one metal to which the single-cell process is 
more particularly applicable, it is copper, especially its 
reduction from the more ordinary salts : where the acid in 
conjunction with the metal is not worth preserving, the 
employment of the zinc single-cell apparatus, unless under 
particular circumstances, is better dispensed with. The 
reduction of the metal by iron is, for its economy, to be 
preferred to all other methods in those cases where it is 
applicable. Yet upon the whole, as the single battery pro- 
cess is suitable to every possible case, for which the reduction 
of copper can be required, it as a general rule must still 
supersede the other modes of working in copper. The 
expense of each process has already been noticed when 
treating of the general means by which the expense of 
working in metals is calculated, and as the reduction of 
copper is there taken as an example, it would be but a vain 
repetition again to detail it. 



206 BLACK LEAD BRONZE. GREASE BRONZE. 

For copies of medals, and other works of art, a copper 
surface is not always desirable, bronze having a much better 
appearance, and this may be communicated in various ways. 
The one most generally adopted is the following : — The 
medal is covered over with oxyde of iron, and placed in a 
muffle, and in this state exposed to heat ; when removed 
from the fire, it simply requires to be. brushed, and is then 
fit for the cabinet. 

Generally, however, we adopt more ready methods of 
producing the bronze ; one of which is to brush the medal 
over with black lead, immediately upon its removal from 
the solution. It is then placed on the fire till moderately 
heated, when it may be smartly brushed with a hog's-bristle 
painting-brush, the slightest moisture being used at the same 
time, in order to remove the black lead. An uniform shining 
bronze is thus obtained. There is no method of bronzing to 
be preferred to this for beauty, as a medal not two hours old 
displays the fine colour of antiquity so much prized by nu 
mismatists. In these operations, I believe an oxyde of 
copper is produced, to which the effect is mainly to be 
attributed. If the metal has been allowed to remain out of 
the solution for some time before the bronze is given, it is 
not found to take so readily. In that case it is better most 
thoroughly to clean the surface, and then to proceed as 
before. 

The application of a very minute quantity of grease, or 
wax, much improves the bronze. This is, however, un- 
necessary when the copper has been deposited on a mould 
consisting in part, or entirely, of these substances ; but in 
other cases, the application is very advantageous. Grease 
or wax alone, when applied in an infinitesimal quantity over 
the surface of a medal, enables it to take a fine bronze when 
simply heated to a proper temperature. We cannot readily 
give the precise temperature at which the best effect is 
produced, but, as a general rule, the heat should be applied 



METHOD OF BRONZING COPPER. 207 

just so high, and for such a length of time, that smoke from 
the incipient decomposition of the grease begins to appear. 
A greater heat causes the copper to blister, but if removed 
at that precise moment the surface will be beautifully oxy- 
dated. The perfection of this kind of bronzing, as well as 
that of the black-lead, depends in great measure on the skill 
of the operator, and the effect may be much enhanced by 
rubbing the medal with a nail-brush containing plenty of 
bristles, and finishing it with a little whiting, placed on a 
piece of wash-leather. 

The French have a method of bronzing cliche es, which 
is very effective. They are sometimes so readily mistaken 
for copper, that a gentleman placed what he conceived to be 
a copper medal into a trough to obtain a reverse, when to 
his astonishment, on the removal of the mould, instead of 
a copper medal he found he had a leaden one. The mode 
by which this bronze appearance is given, is to moisten the 
surface with a little spirits of wine, and at the moment of 
drying, dusting it with a little red chalk, modified in colour 
with a portion of black-lead, and then with a good puff 
dispersing any superfluity that may have been employed. 
This process might also be employed for copper medals, but 
the colour is, perhaps, not so fine as by the process already 
detailed. There are other modes of bronzing clichees which 
are not applicable to copper, such as dipping them in a 
solution of the binacetate of copper, acidulated with acetic 
acid, by which means the medal reduces a=small portion of 
copper, and therefore has all the appearance of a copper 
medal. 

Instrument-makers have a mode of bronzing the copper 
which is used for binding-screws and other parts of their 
apparatus. It is simple and effectual, for the metal is simply 
to be rubbed over with a little weak solution of platinum, 
when the copper, or a portion of it, is dissolved, and an 
equivalent proportion of platinum is thrown down. They 



208 SULPHURET BRONZE. 

generally protect this from change by varnish, but this 
should never be applied to delicate impressions. A solution 
of gold would answer the same purpose, did not its value 
prohibit its application. 

Another valuable method of bronzing is the application 
to the metal of a very weak solution of the hydro-sulphate 
of ammonia, or the sulphuret of potassium, when a sulphuret 
of the metal is obtained, which is of a very beautiful colour. 
If the solutions are used too strong, a thick layer of sulphuret 
is produced, which much detracts from the beauty of the 
medal as a work of art. 

A new mode of bronzing has lately been introduced by 
Mr. De la Rue, for which he has obtained a patent. The 
metal to be bronzed is first of all blackleaded, and then 
placed in a basin of water. Upon the water a few drops of 
white hard varnish, to which "had been previously added a 
little oil of lavender, are then placed. The varnish is gently 
skimmed till it is very thin, when, upon the principle of 
Newton's rings, it exhibits its colours. The blackleaded 
object is then raised from the water and draws with it the 
iridescent film, and finally the object is very slowly dried, 
when a very beautiful bronze is exhibited. When this 
film is fixed upon paper it is called opaline, and when 
brought before the public, will doubtless be much employed. 

The object of all these methods is to throw up the fine 
workmanship — a result which is efficiently obtained in the 
colour given by the methods which have been detailed ; the 
choice of these is left to the operator, but perhaps none 
excels, or even equals, the mode of bronzing by black lead, 
or grease, when those operations are performed with care, 
and in the manner which has been described. 

(178.) Zinc may be reduced in the bright metallic state 
from a variety of solutions, as the oxyde of zinc is soluble in 
a great number of acids. The sulphate of zinc, however, is 
by far the most common salt of this metal, and it is formed 



CHLORIDE OF ZINC. 209 

tolerably pure and in large quantities during the employ- 
ment of galvanic batteries. The solution of the sulphate of 
zinc may be of any strength, but perhaps the stronger is to 
be preferred. It should be as neutral as possible, and it is a 
good plan to add a little oxyde of zinc to the sulphate, but 
this salt always reddens litmus paper. Sulphate of zinc is 
best formed for electro-metallurgy in a series of my galvanic 
batteries, gradually decreasing the rapidity of the process 
towards the termination until zinc begins to be deposited. 
Zinc can only be reduced practically by the battery process. 
In the trough it is as well to use a very large zinc positive 
pole, and take especial care to cause a proper diffusion of 
the new sulphate of zinc, and the compound trough appa- 
tus is particularly commendable for this process. Hydrogen 
has a considerable tendency to be evolved from the solution. 
The battery should be small, as the galvanic power should 
be feeble, and the resistance in this case should be rather in 
the battery or the connections than in the positive pole. In 
some cases the positive pole of zinc might be platinized, so 
that any free acid may be immediately neutralized. Reduced 
zinc may be thrown down in a very flexible state, and is far 
more slowly acted upon in dilute sulphuric acid than com- 
mon zinc. 

The ammonio-sulphate of zinc may be made by adding 
liquor ammoniae to a solution of sulphate of zinc. It is a 
good conductor, and may be used with a zinc positive pole. 
It is a tolerably good solution of the metal to obtain the 
reguline deposit. 

Potash added to a solution of sulphate of zinc throws down 
a precipitate which is soluble in excess. The zinc is not so 
readily reduced from it as from the sulphate, and it requires 
a series to effect that object. The zinc positive pole does 
not freely dissolve in it. 

The chloride of zinc is usually formed by dissolving the 
metal in muriatic acid, when hydrogen is most abundantly 

11 



210 NITRATE OF ZINC, ETC. 

evolved. It is now occasionally used in surgery as an escha- 
rotic, and it may be employed for electro-metallurgy in the 
same way as the sulphate of zinc. It is a good solution, but 
possesses no particular advantages. If chloride of zinc is 
formed by the galvanic battery, it is better adapted for elec- 
tro-metallurgy. This, perhaps, is the best solution for 
obtaining crystals of zinc. 

The nitrate of zinc formed by the action of nitric acid on 
zinc is the very worst salt I have tried for the reduction of 
the metal in the reguline state. 

The oxyde of zinc is very soluble in muriate of ammonia. 
There is a great tendency to the evolution of j hydrogen in 
this solution, and therefore it is not a good compound for the 
reduction of the reguline metal, though it is well adapted 
for obtaining zinc sponge in large quantities. 

The acetate of zinc may be formed by digesting oxyde of 
zinc in pyroligneous acid, or by making zinc the positive 
pole in that fluid. It is a very good solution for obtaining 
reguline metal by the single battery process. 

The tartrate of zinc formed as the acetate, possesses no pe- 
culiar advantage for electro-metallurgy. 

The potassio-tartrate of zinc may be made by boiling the 
oxyde in cream of tartar, or by making a plate of zinc the 
positive pole in a solution of bitartrate of potash. The zinc 
positive pole does not freely dissolve in it. 

The hydriodate of zinc is a good solution for electro- 
metallurgy. It is best formed by galvanism, by using a zinc 
positive pole in a solution containing a very minute quantity 
of iodide of potassium and a very large quantity of undis- 
solved iodine at the bottom of the vessel. The iodine will 
at last be entirely taken up and a corresponding quantity of 
iodide of zinc formed. 

The zinco-cyanuret of potassium may be formed by either 
digesting the oxyde in the cyanuret of potassium, or galva- 
nizing a plate of zinc in a solution of the cyanuret. It 



REDUCTION OF ZINC. 211 

forms octohedral crystals, but it is a difficult salt to decom- 
pose, requiring a series of batteries for its reduction, and it 
is difficult to obtain even a small amount of zinc from it. 

The reduction of the zinc is not of much importance in it- 
self, although very interesting when considered in reference 
to the plates of galvanic batteries ; for if one battery in a 
compound series, from any cause, has the whole of its excit- 
ing fluid neutralized, then will that cell be in the same con- 
dition as the apparatus employed for the reduction of the 
zinc, and zinc will immediately be deposited on its negative 
pole. This will occur with all the forms of batteries now 
employed, although it is a property of no consequence, as 
the action of the battery ought to be stopped before it has 
so thoroughly exhausted itself. When this deposit takes 
place, it can readily be removed by placing the plate in 
contact with any metal which can act as a negative plate to 
it. The necessity of this arises from the difficulty with 
which pure zinc is dissolved in acid. As soon as a dozen or 
more batteries, arranged as a series, have the acid of their 
exciting fluid saturated with zinc, the zinc will be deposited 
on the negative plate, if a single battery only out of the 
whole number contain any acid ; thus eleven batteries out 
of twelve may have their negative metal thickly coated with 
a very beautiful and perfect deposit of zinc, whilst the last 
will not have the smallest trace upon it. Zinc is never found 
in all the batteries of a series. There will be some curious 
matter to be discussed when we have to describe the reduction 
of alloys. 

In the reduction of zinc from any salt there is a difficulty 
to be encountered which will be explained when treating of 
the reduction of alloys, for reguline zinc of the best quality 
may go down at first, but afterwards one of the varieties of 
the spongy deposits will take place. This alone forms a 
great impediment to the reduction of zinc on a large scale. 

The reduction of zinc is generally a disadvantageous pro- 



212 REDUCTION OF CADMIUM. 

cess, as the cost of its deposition is the same as that of copper, 
from their voltaic equivalents being alike. Zinc, however, 
is worth but threepence a pound, whilst the value of copper 
is a shilling. 

The material which is sold under the name of galvanised 
iron, is not iron coated with zinc by the voltaic process ; in 
fact galvanism has nothing to do with it. The iron is very 
thoroughly cleansed by acid, and then dipped into a bath of 
melted zinc, and moved about till a coating is effected. 
There is another variety called galvanized tinned iron, in 
which the iron is first coated with zinc, and then dipped into 
melted tin. The use of the word " galvanised" is highly 
improper in both these cases, because people are prone to 
think that the process has been effected by galvanism. 
These processes for zincing iron are extremely valuable, 
and should be extensively employed as a substitute for 
paint. 

(179.) Cadmium has a variety of soluble salts, of which 
the sulphate, ammonio-sulphate, and chloride, are the only 
ones I shall notice. The sulphate may be employed with a 
cadmium positive pole and a small battery. For small nega- 
tive surfaces, one of the odds-and-ends' little glass batteries, 
described when treating of the reduction of platinum, is well 
adapted. Cadmium of good quality does not readily go 
down from the sulphate. 

The chloride of cadmium may be made by galvanism, by 
arranging a piece of cadmium as the positive pole in dilute 
muriatic acid. The chloride of cadmium behaves much 
in the same way as the sulphate. Cadmium, however, has 
a tendency to be thrown down in a peculiar state between 
the sponge and the crystalline deposits, and hydrogen has a 
considerable tendency to be evolved from both this and the 
last solution. 

The ammonio-sulphate of cadmium may be. formed by 
adding ammonia to a solution of the sulphate, as the pre- 




REDUCTION OF IRON. 213 

te is soluble in very small excess of the precipitant. 
It may be employed with a cadmium positive pole in con- 
junction with a small odds-and-ends' battery. This is the 
best solution for obtaining the reguline deposit, which may 
be easily thrown down in a flexible state from it. 

The reduction of cadmium might be followed with advan- 
tage as an equivalent of power ; value J^ of a penny would 
reduce about 56 grains of the metal ; so that a pound of 
cadmium obtained by the voltaic force would only require 
about sixpence to be added to the cost of the metal, which, 
being scarce, is considerable. 

(180.) The salts of iron have a strong tendency to be 
peroxydised, in which state they cannot be reduced by the 
voltaic current. We must use, therefore, the proto-salts, 
of which the proto-sulphate of iron is a good example ; 
this is prepared very carefully for the use of chemists, 
and the reduction of metallic iron may take place from a 
solution of the proto sulphate. The metal upon which the 
deposit is to be effected, is connected with the zinc of the 
battery, whilst an iron nail is connected with the silver ; as 
the source of power, a relatively small single battery will 
suffice, and the silver need not be larger than the negative 
pole in the trough. The nail is to be just so far dipped 
into the solution, that the minutest quantity of hydrogen, 
or none at all, is evolved from the metal to receive the 
iron ; and after the lapse of a short time, the negative 
metal will become coated with metallic iron. The reduced 
metal is brighter, and rather whiter than polished steel, 
but it soon tarnishes in the air. 

Proto-chloride of iron may be formed by dissolving iron 
in muriatic acid ; it forms a perfectly neutral salt, and is 
well adapted for the reduction of the metal. It may be 
reduced by either battery process, of which the single 
battery will always suffice. The hydrogen has not so great 
a tendency to be evolved as in the sulphate, and the 



214 CITRATE OF IRON, ETC. 

metal goes down freely from it. This is an excellent solu- 
tion, perhaps the best for the reduction of this metal. If 
the iron is removed from the plate on which it is deposited, 
the surface next to the negative pole is polished if the 
original is so also ; and very thin layers of this metal have 
a very fair cohesion, inferior, however, to the rolled iron of 
commerce. 

Iron may be reduced, but only in the minutest quantity, 
from the ferro-eyanate of potash, which is, therefore, useless 
for electro-metallurgy. 

The compounds of iron with the vegetable acids may be 
employed for electro-metallurgy. The citrate may be made 
by arranging a plate of iron as the positive pole in a solution 
of citric acid ; but it is difficult of decomposition, requiring a 
series of batteries. 

The proto ioduret of iron, as used in medicine, may be em- 
ployed for electro-metallurgy. It is not, however, so good 
a compound as the chloride for these purposes. 

Iron reduced by electricity has not yet been examined 
as to its magnetic properties, and, doubtless, pure iron 
obtained in this manner must possess peculiar properties 
still undiscovered. 

The reduction of iron, in a pecuniary point of view, is 
the very worst process in the whole range of electro-me- 
tallurgy ; for the metal is worth scarcely anything in com- 
parison with others we have had to treat of. The iron- 
masters, doubtless, will sleep in perfect security when they 
are told, that for one equivalent of galvanic power de- 
rived from my battery costing fa of a penny, but 28 grains 
of iron are reduced ; so that the reduction of lib. of iron, 
worth about one penny, would cost more than one shilling 
for the bare materials used in its reduction, to be added to 
the value of the metal. Under this aspect of affairs, not only 
the blast, but even the puddling and melting furnaces, are 
likely to continue to send forth their pestiferous fumes by 



REDUCTION OF TIN. 215 

day, and their pandemonium-looking flame by night, cor- 
rupting the atmosphere, to the injury of vegetation, as well 
as to the detriment of the health of all living beings. 

(181.) Tin is a difficult metal to manage, because the 
transition from the decidedly spongy state to the crystalline 
is so rapid, that we can scarcely hope to attain any amount 
of reguline metal. The salts which I have tried are nume- 
rous, but they all have the same general characters. The 
muriate is the most common of the salts of tin. It yields 
very fine crystals when decomposed by a small odds-and- 
ends' battery, with a tin positive pole. If the battery is 
very active, the tin positive pole large, and the solution 
strong, the growth is marvellous ; a little point will pre- 
sent itself on the negative metal, which rapidly increases, 
and in a few seconds will grow to the positive pole. If 
during this rapid growth the positive pole be moved, the 
crystal will follow it. 

The finest crystals are obtained, however, by the strongest 
neutral metallic solution, and a very low action in the battery. 
The deposit is certainly very beautiful. The spongy deposit 
of tin is very peculiar, and the electro-metallurgist is apt 
to see it much oftener than he wishes ; for that light, floc- 
culent spongy deposit, which is frequently observed dur- 
ing the action of the battery, is nothing but metallic tin, 
arising from zinc clippings mixed with solder being melted 
with the rough spelter ; if a little of this mass be squeezed 
between the fingers into a mass, and then struck and rubbed 
against anything hard, a bright metallic surface will be ex- 
posed. 

The sulphate of tin may be formed by digesting the proto- 
oxyde in dilute sulphuric acid ; it is rather a better salt than 
the other ; and might be used for some purposes to coat iron. 
A kind of lesser crystalline deposit may be obtained from it, 
but not sufficiently good to form a tin medal. 

The oxalate of tin and acetate of tin are made in the same 



216 REDUCTION OF LEAD. 

way as the sulphate. They are not quite such good con- 
ductors as the sulphate, and do not yield good reguline tin 
to any extent. 

The potassa solution of the oxyde of tin is a bad con- 
ductor, requiring an intense battery for its decomposition. A 
good thin layer may be deposited from the solution, but I 
have never made a medal with it. 

The oxyde of tin dissolved in cyanide of potassium is 
difficult of decomposition, and does not yield any amount of 
tin. 

I have tried a great variety of other mixtures of these 
salts, as oxyde of tin with cream of tartar, sulphate of alu- 
mina, chloride of sodium, hydriodate of potash, &c, &c, 
without any satisfactory result. 

The reduction of tin by galvanism cannot be considered 
an advantageous process, from the low value of the metal. 
One eqivalent of power, costing 2V of a penny, will reduce 
about 58 grains of tin, making the cost of the power, about 
sixpence a pound, to be added to the value of the tin. 

(182.) Lead has but few soluble salts, of which the ace- 
tate, the nitrate, and plumbo-cyanide are the principal which 
deserve attention. 

The acetate is abundantly soluble, and may be employed 
for the reduction of the metal. It may be used with a lead 
positive pole, connected with a small battery. Lead has 
such a tendency to be deposited in crystals from this solution 
and the crystals grow so rapidly and to such a size, that it 
is in vain to attempt to obtain the reguline deposit from 
it, especially as the gradation from the spongy to the reguline 
deposit is very close. The crystals of lead as reduced by 
zinc form what h termed the lead tree. To produce it a small 
piece of zinc is suspended in a bottle, containing a clear 
solution of acetate of lead, when speedily the metal begins to 
be thrown down, and continues to be deposited in the beau- 
tiful forms to which the name of the lead tree is given. The 



METALLO-CIIROMES. 



217 



experiment may be varied by using a copper wire round the 
zinc, and passing it to the bottom of the vessel, when the 
lead will also be deposited on the copper wire ; in a solu- 
tion of acetate of lead, the positive pole becomes encrusted 
with a deposit, w T hich is the peroxyde of that metal. I 
have observed a similar deposit in the decomposition of 
other metallic salts, but as none have been turned to any 
account but this, the fact need not be more particularly al- 
luded to. The production* of this oxyde has been used by 
Mr. Gassiet to form metallo-chromes, which, for striking 
effect and beauty of colours, are unequalled by any other 
work of art. They are formed by throwing down a deposit 
of this compound of various thicknesses, on a plate of polished 
metal (burnished steel answering best). The difference in 
the thickness of this deposit is accomplished by placing the 
plate of steel at unequal distances from the negative pole. 
The negative pole should consist of a copper disc made 
slightly convex, which at once very effectually causes a 
variation in the distances. The exact modus operandi, 
which Mr. Gassiot recommends, is to place the polished 
steel plate (p), in 

a solution of ace- Fl 9' 34 - 

tate of lead, and 
over that a piece 
of card, with som e 
regular device cut 
out (c). A small 
rim of wood (w) 
should be placed 
over the card, and 

the circular copper disc (d) (which is represented in the wood- 
cut on one side) over all. On contact being made from 
5 to 20°, with 2 or 3 cells of a small battery — the steel 
plate being connected with the silver, the copper disc with 
the zinc, the deposit will be effected, and a series of those 

11* 




218 METALL0-CHR0MES. 

exquisite colours will delight the operator, which arise from 
the decomposition of light, by a layer of different thicknesses 
of peroxyde. By reflected light every prismatic colour is 
seen, and by transmitting light a series of prismatic colours, 
complimentary to the first series, will appear occupying the 
place of the former series. 

The best way of viewing these beautiful fairy forms is to 
place the plate before a window, and incline a sheet of white 
paper at an angle of 45° over thfc plate, when if the plate be 
viewed at a considerable angle the colours appear to stand 
boldly forth on a white ground.* 

The tris-nitrate of lead forms rather a better salt for the 
reduction of reguline metal. It may be used in the same 
way as the acetate, but I have only reduced small portions 
of reguline lead, that I could strip from the negative pole 
from it. 

From the plumbo-cyanide of potassium 1 have reduced 
reguline lead of good quality, which could be stripped from 
the negative plate, still only in small quantities ; probably 
from the insolubility of the oxyde of that metal at the posi- 
tive pole. 

The reduction of lead by galvanism is not, independently 
of the difficulties attending it, a good process, because the 
value of the metal is low, yet inasmuch as- we obtain for one 
equivalent of power 104 grains of lead, that would rather 
lessen the cost of the process. 

(183.) Antimony is one of those metals by no means de- 
serving more than a cursory glance. The only solution 

* I have formed metallo- chromes analogous to those described in the 
text, in a very different way, yet dependent on the same principle. A 
plate of polished copper placed over a card device, and then exposed to 
iodine, becomes coated with a thin film of apparently iodine of copper, 
which shows the prismatic colours very beautifully ; yet far inferior to 
those formed by peroxyde of lead. This experiment may be varied in 
many ways. 



REDUCTION OF ANTIMONY, BISMUTH, ETC. 219 

which I shall notice is that of the potassio-tartrate. It is 
tolerably well adapted for the reduction of the metal in the 
reguline state. It is not very readily decomposed, requiring 
a couple of batteries with an antimony positive pole. The 
metal is then thrown down slowly, but forms a brilliant 
deposit, which may be stripped from the negative pole. An- 
timony, instead of being deposited at the negative pole, in 
some cases combines with the hydrogen, and is evolved as 
antimoniuretted-hydrogen gas. 

(184.) Bismuth is another metal, to the characters of 
which, in an electro metallurgical view, very little interest 
can be attached. Its super-nitrate is a soluble salt, and may 
be employed with a positive pole of the same metal attached 
to a single battery. The deposit, however, from this solution 
has a tendency to assume a mixture of the sponge and crys- 
talline deposit. 

The tris-nitrate, or medicinal salt of bismuth, is an in- 
soluble salt, and therefore inapplicable for our purpose. 

The iodide of bismuth is soluble in excess of iodide of 
potassium, but I have not turned it to any good account. 

The potassio-tartrate of bismuth may be soluble by making 
a piece of bismuth the positive pole in bi-tartrate of potash. 
It may be employed with two batteries arranged as a series. 
It is not a ready conductor. The metal is reduced but slowly 
from it. A white powder forms upon the positive electrode, 
which at length stops the action. So little importance is 
attached to the reduction of this metal in the reguline state, 
that I have not bestowed much time upon it. 

(185.) Uranium is another metal which I have endea- 
voured to deposit from its nitrate, but without success ; in 
fact, being a per salt it was not likely to be reduced. I have 
not succeeded in procuring any proto salts of uranium on 
which to experiment. 

(186.) Arsenic is a metal not likely to be of much value 
for electro-metallurgy, yet there are some important circum- 



220 DETECTION OF ARSENIC. 

stances to be noticed in its characters when subjected to the 
voltaic fluid, which require some notice in this place. 

The oxyde of arsenic or arsenious acid is frequently em- 
ployed as a means of destroying • animal life, and though its 
means of detection when improperly administered, are more 
simple and certain than that of any other poison whatever, 
the minds of chemists are continually being directed to some 
new mode of effecting that object. As far as the voltaic 
power may be brought to bear in the detection of this metal, 
I shall briefly notice the subject, but no further. 

Arsenious acid is not very soluble in water, and is but a 
bad conductor of the voltaic force. It may be decomposed by 
a series of batteries with platinum electrodes, oxygen being 
evolved at the positive, and the metal reduced at the nega- 
tive electrode. The hydrogen, however, in this case, not 
only reduces a part of the metal, but combines with another 
part, forming arseniuretted-hydrogen gas. This gas has a 
peculiar alliaceous or garlicky smell, which is a good charac- 
teristic of its presence. If a small jet is inflamed and a 
cold object placed over it, arsenious acid is deposited, but, 
however, if the cold object be depressed so as to cut a portion 
of the flame, metallic arsenic will be reduced. 

The phenomena appertaining to this gas were first applied 
ingeniously by Marsh to the detection of arsenic. He em- 
ployed zinc, dilute sulphuric acid, and the suspected liquor, 
and then tested the hydrogen when inflamed, in the manner 
just pointed out. He describes a considerable number of 
pretty contrivances for effecting that object ; sometimes he 
uses a tube simply bent upon itself into one end of which a 
stop-cock and jet is fixed, the other being left free ; some- 
times he dilates his tubes into a bulb. A great variety of 
apparatuses are described for the production of the gas. All 
these forms are well adapted for the detection of arsenic 
when they are not wanted for organic mixtures, but when 
the contents of the stomach have to be examined, they are 



REDUCTION OF ARSENIC. 221 

generally but ill adapted from the froth that generally ensues. 
When arsenic is taken into the stomach, that organ not liking 
its new customer endeavours to remove it out of contact by 
pouring out a large quantity of mucus which envelopes the 
poison and protects the stomach in some degree from its in- 
fluence. The cunning chemist should mechanically dissect 
from this secretion the white powder, and subject that to ex- 
periment, for it is only in those cases where poisoning is 
effected by very minute quantities, that the poison is not at 
once seen as a white powder. Having separated it, it is to 
be dried at a gentle heat, and distilled from the bottom to 
the upper part of a test tube by means of a spirit lamp when 
it is ready for the various experiments to which the operator 
is inclined to submit it. If we choose the arseniuretted- 
hydrogen test the vessel should be capacious, a phial with a 
piece of glass tube drawn to a point and inserted in the cork, 
is well adapted. 

Zinc is apt to contain arsenic itself, therefore it would be 
better always in judicial cases to employ that reduced by the 
voltaic agent ; the sulphuric acid is also apt to be intermixed 
with small portions of this metal, for which reason both 
should be tested before they are used. We should never be 
satisfied with this test alone, unless we can obtain arsenious 
acid sufficient to test with the ammonio-nitrate of silver, 
ammonio-sulphate of copper, and sulphuretted-hydrogen, for 
not only may a little black crust of antimony be mistaken for 
arsenic, but even a little animal matter may give a similar 
deposit. 

Morton, in order to overcome the errors from impurities 
in the acid and zinc, proposed to subject the suspected fluid 
to an intense galvanic battery, and then examine the hydro- 
gen. The only difficulty in this proceeding is the imperfect 
conducting character of the compound to be operated on. 
This difficulty might be overcome by the addition of pure 
potash. 



222 REDUCTION OF ARSENIC. 

I have now to call attention to the following mode of 
taking advantage of the opportunity afforded to us of sub- 
jecting the suspected fluid to a long continued galvanic cur- 
rent of but feeble quantity ; for by that means we should be 
enabled to determine the presence of arsenic, by heating the 
negative pole in a test tube when arsenious acid would be 
formed. This would be deposited at the upper part of the 
tube, and on being tested would give the most unequivocal 
signs of the presence of that metal. This, although by no 
means the most delicate is by far the most satisfactory pro- 
ceeding we can adopt, for we need not introduce into the 
suspected solution, any new substance, so that not a shadow 
of doubt could be thrown on the accuracy of the result if 
arsenic be obtained : if, however, we do not succeed in 
obtaining arsenic, it is not an infallible proof of its absence. 
By this plan the following characteristics are shown : 

(a.) The reduction of the metallic arsenic on platinum. 

(b.) Its volatility and conversion into arsenious acid, leav- 
ing the platinum clear. 

(<?.) The yellow precipitate of arsenite of silver w T ith am- 
monio-nitrate of silver. 

(d.) The green precipitate of arsenite of copper with am- 
monio-sulphate of copper. 

(e.) The yellow sulphuret of arsenic with sulphuretted- 
hydrogen. 

In conducting the process, a series of not less than a dozen 
batteries should be used, and the process should be continued 
till the negative platinum pole (a wire will suffice) becomes 
coated with metallic arsenic which presents a somewhat bright 
black appearance. The wire is then simply to be coiled up, 
placed in a test tube, and heated over a spirit-lamp when the 
arsenious acid will be seen at the upper part of the tube, as 
small white crystals, which are to be dissolved and subjected 
to the other solutions. By continuing this process suffi- 
ciently long, the whole or the greater part of the arsenic will 



REDUCTION OF COBALT. 223 

be reduced, and then would the medical man be enabled to go 
into court armed not only with the reasons in his breast, but 
the arsenic in his hand. 

If a copper or a silver positive be used in a solution 
containing arsenious acid, the yellow or green precipitate will 
be formed ; but they are not satisfactory modes of detecting 
the presence of that metal. 

(187.) I have endeavoured to reduce tungsten from tungstic 
acid by using a small platinum wire as a positive pole in the 
solution of the acid. It is but an imperfect conductor, and 
requires a series of nine or ten batteries. I have not, how- 
ever, succeeded in obtaining any metal from the acid. 

(188.) Cobalt may be reduced from its chloride, to which 
excess of ammonia has been added, by using a cobalt positive 
pole connected with a series of batteries, when the deposition 
will take place upon the negative plate, which may consist of 
copper. The reduced metal is white, but it is not thrown 
down freely. The chloride of cobalt alone, seems only to 
yield an oxyde at the negative pole. The cobalto cyanuret 
of potassium formed by digesting oxyde of cobalt in the 
cyanuret, yields, by decomposition with a compound battery, 
some metal, but hydrogen has a great tendency to be evolved 
from this solution. 

(189.) Manganese has been attempted to be reduced from 
the sulphate or chloride with signal failure, for the hydrogen 
has a decided preference to be evolved, even from a polished 
surface, rather than to reduce the metal. At the positive 
pole an iridescent deposit, apparently a peroxide, is abun- 
dantly thrown down. 



224 



CHAP. V. 



ON THE REDUCTION AND ANALYSIS OF ALLOYS. 

Law for the completion of the voltaic circuit through various solutions, 
190. Table of relative facility of decompositions, 191. 

(190.) Hitherto we have only considered the formation of 
single salts, and the reduction of simple metals. We have 
now to discuss the important question, whether two or more 
metals can be reduced at the same time ; and whether the 
metals can be thrown down conjointly with other bodies. 
This, considering the amazing number of solutions, becomes 
a very complex question ; and only a general outline of the 
principles regulating these phenomena can, in the present 
state of our knowledge, be attempted. In entering upon this 
subject I began by selecting metals far apart in the facility 
of their reduction by hydrogen ; thus, solutions of the salts 
of zinc and copper, being mixed, only copper was reduced 
at the negative pole. Without detailing a mass of similar 
experiments, I shall at once state, as a fundamental prin- 
ciple, an absolute law derived from a most extensive exami- 
nation of the voltaic force, that, the voltaic circuit is 
invariably completed in that mode which offers least 

RESISTANCE TO THE PASSAGE OF THE FORCE. That is tO 

say, that if a great variety of roads are offered by which 
that object may be effected, that the force, provided the 
road be large enough, would pass exclusively through the 
one offering the least resistance. To take an example of 
this, add to strong nitric acid, chloride of gold, chloride of 
platinum, chloride of palladium, and any other metallic salt 



REDUCTION OF ALLOYS. 225 

you have at hand that will remain soluble in the acid, — and 
then decompose the mixture between platinum poles, you 
will find that the circuit will be completed alone through the 
nitric acid. You may analyze your experiment by placing 
each salt in a separate vessel, with precisely the same result, 
as the current will alone traverse the fluid easiest of decom- 
position, provided that the electrodes exposed to that fluid be 
sufficiently large. By acting upon this principle the student 
will perceive that one body might be separated from another, 
or even from a variety of others : thus, if brass is dissolved 
in dilute sulphuric acid by the aid of the voltaic force, the 
precipitate at the negative pole will by management be pure 
copper only. A person who accidentally stumbled upon this 
result, bought a large quantity of that alloy in the vain hope 
of amassing a fortune by what he conceived to be a transmu- 
tation of metal, though he doubtless must have discovered 
at last that he only obtained the copper originally contained 
in the alloy. 

Whatever experiments are detailed relative to the reduc- 
tion of the alloys, the converse of them applies exactly to the 
separation of one metal from another. Before we proceed 
further in our inquiries we should form a list of the fluid 
roads by which the voltaic circuit may be completed, and 
place them in the order of the facility with which the passage 
is made by the voltaic force. As it has been shown that the 
decomposition of various salts is attributable to the secondary 
action of hydrogen, termed electro-chemical decomposition, 
the first thing that we have to determine is the point, in 
various cases, at which hydrogen would rather be evolved 
than decompose the metallic salt. But the very construction 
of my battery depends upon the primitive fact that different 
metals, and even the same metals under., different circum- 
stances, evolve hydrogen from the same solution with various 
facilities. It is natural to suppose then, if our law for the 
passage of the fluid be correct, that there are some cases 



226 REDUCTION OF ALLOYS. 

where the nature of the negative plate, on which the reduction 
of the new deposit takes place, influences the result ; this is 
actually found to be the case, for sometimes in the self-same 
solution, when a smooth negative plate is used, the circuit 
would rather be completed by reducing a metal, but when 
a rough plate is employed, by the evolution of the hydrogen. 
This most interesting fact is in no instance better shown 
than in a slightly-acidulated solution of sulphate of zinc, from 
which bright zinc will go freely down on smooth platinum, 
whilst from platinized platinum the hydrogen would be 
evolved. This experiment may be varied a hundred ana- 
logous ways, with results at one time in favour of the evolu- 
tion of the gas, at another of the removal of the gas by the 
decomposition of some compound. This at once introduces 
a new element into our reasonings, for we should form a 
table showing the relative ease with which hydrogen is 
evolved from various bodies ; the top of this table is either 
platinum, palladium, or silver, in the infinitely divided state 
used for my battery : but the exact relation which the per- 
fectly divided metals bear to each other, or even to themselves 
in other states, in different solutions, or even in the same 
solution, at different temperatures, I am unable at the present 
time to give ; indeed it would be a work of such mechanical 
labour, that I should not with my present avocations feel 
warranted in undertaking it. 

The evolution of hydrogen gas from any given solution 
being taken at unity, as soon as the case of its evolution is 
less than any other mode by which the circuit may be com- 
pleted, the evolution of the hydrogen is ceded to that mode : 
generally, the hydrogen if not evolved, reduces some oxygen- 
ated body or some metallic salt, and then the analogy is kept 
up by its reducing that salt, which yields its metal most 
readily to the gas. The gas is perhaps easiest evolved from 
muriatic or dilute sulphuric acid. 

(191.) We here require another extensive table, showing 



REDUCTION OF ALLOYS, 



227 



the relative ease with which bodies are reduced by hydro- 
gen ; perhaps nitric acid is at the top of the list ; then follow 
the salts of some of the nobler metals, whilst salts of zinc 
and numerous other metals are below the evolution of hydro- 
gen from sulphuric acid :- — 



Nitric acid. 
r Gold chloride. 
< Palladium nitrate. 
f Platinum chloride. 

Silver nitrate. 

Copper sulphate. 

Tin sulphate. 



Hydrogen dilute sulphuric acid. 

Cadmium sulphate. 

Zinc sulphate. 

Nickel sulphate. 

Iron sulphate. 

Manganese sidphate. 

Salts of alkalies, generally. 



Hydrogen easily reduces the per salts of iron into proto 
salts, — a fact of considerable importance in many electro- 
metallurgic operations. 

The above is given as a rough specimen of a table show- 
ing the relative facility by which the removal of gas may be 
effected ; therefore, supposing our electrodes were sufficiently 
large, and an ample supply of solutions of the various salts 
were afforded, but one compound would be decomposed at one 
time. 

However, suppose by using an intense voltaic current, we 
compel such a quantity of the force to pass from a small elec- 
trode, that any one compound body in its vicinity is insuffi- 
cient to complete the circuit it would then be completed 
through two, three, four, or more bodies, and it would reduce 
them all at once ; thus, our mixture of metallic salts with 
nitric acid, decomposed by an intense current with small elec- 
trodes, had a great variety of metals reduced, whilst on the 
increase of the poles the circuit was entirely completed 
through the nitric acid. In the same way I have decomposed 
twenty different solutions, arranged not as a series but as 
one decomposition cell. 

As a general principle, to obtain a deposit of two or more 
bodies on any negative pole, we must use a quantity of the 



228 REDUCTION OF ALLOYS. 

voltaic force, more than sufficient to reduce the elementary- 
substance from the compounds most readily decomposed. 
By the first law regulating the quality of metal reduced by 
the voltaic current, the metal is always reduced as a sponge 
when hydrogen is evolved from the negative plate ; therefore, 
it would be impossible to obtain a reguline alloy in a solution 
of any two metals, one of which is above, the other below, the 
evolution of hydrogen, from the particular negative pole we 
employ in these solutions. 

Such is a rough sketch of the principles to be pursued for 
the reduction of alloys, but at present practically I have not 
reduced a perfect reguline alloy of any metal, though I feel 
no doubt, by following out the above principles, a person 
might succeed in attaining his object with some metals, by a 
careful examination of their various salts. 

Electro depositions of brass have occasionally been stated 
to be produced, but in these cases the zinc and copper have 
been reduced contemporaneously, and their union has been 
afterwards effected by heat. 

The general principle which regulates the reduction of 
alloys is far more important than for the specific object for 
which it is given ; for the experimenter will find that the 
current will invariably pass through the road which presents 
the least obstacle, be that obstacle solid, fluid, elementary, 
compound, small, or great. 



229 



BOOK THE THIRD. 

:CTRO-GILDIKG f SILVER-PLATING, ETC. 

General directions, 192. Electro-gilding, 193. The auro-cyanide of 
potassium, 194. Apparatus, 195. Copper-gilding, 196. Water- 
gilding, 197. Gilding by amalgamation, 198. Electro-platinating, 
Electro-platinizing, 199. Electro-palladiating, 200. Electro-plating, 
201. Plating by other means than Electro-Metallurgy, 202. On coat- 
ing metals with nickel, 203. On coppering metallic substances, 204. 
On coppering non-metallic substances, 205. On coppering medal- 
lions, 206 ; fruit, vegetables, <fec, 207 ; baskets, 208 ; earthenware, 209. 
On coating metals with iron, zinc, <fcc, 210. Conclusion, 211. 

(192.) The infilming of one metal by m another, is a subject 
of much interest, and the process has received different 
names according to the metal employed for that purpose. 
Thus, when gold is used, it is termed gilding ; when copper, 
coppering ; silver, silvering, or silver-plating, &c. In every 
one of these cases we have to be careful that the two metals 
adhere, and for this purpose we take means to prevent any 
film of air, oxyde, or any non-conducting substance, from 
remaining on the first plate, as that would cause a separation 
between the metals. We apply heat, we scour the plate, or 
where it is possible, we slightly act upon the surface of the 
metal to receive the new deposit, taking care thoroughly to 
wash the metal after this operation. 

(193.) ^Electro-gilding is, in most cases, remarkably easy, 

* Mr. Brayley, librarian to the London Institution, has been so kind 
as to call my attention to a process for electro-gilding practised by Brug- 
natelli, an Italian chemist, and noticed in the Philos. Mag. (First Series), 
1805, vol. xxi, p. 18*7. It is singular that one of the supposed novelties 
of our own peculiar time should be discovered to be upwards of forty 
years old, a circumstance which we must more fully notice when treating 
of the history of electro-metallurgy. 



230 ELECTRO-GILDING. 

for if care be taken to follow the laws which have been 
already detailed, it will be attended with very little trouble. 
The metal to receive the gold, may be either platinum, 
palladium, silver, copper, carbon, gold itself, or indeed 
almost any other metal, when the auro-cyanide of gold is 
employed. The surface should be chemically clean, and 
freed from adherent air, either by plunging it into nitric, 
acid or a solution of potash, or by heating it and then 
quenching it in acid. The smoother the surface, the more 
favourably the deposit will take place upon it, for a very 
rough surface is not quite so well adapted for these opera- 
tions, the hydrogen having a greater tendency to be evolved 
from it. When the metal to be gilt does not decompose 
the solution of gold, the solution may be stronger. When, 
on the contrary, the metal acts upon the solution, it must 
be weaker. The electrical current must be suited to these 
varying circumstances, and in general but a feeble current 
is required. 

Pursuant to the plan I have already laid down, the best 
process in each respective department of electro-metallurgy 
will alone be detailed ; and those who desire to use other 
solutions or other processes, are referred to the second book 
of this work, in the four chapters of which he will find such 
information as will enable him to make the alterations he 
desires with profit and success. 

(194.) For all cases of electro-gilding the auro-cyanide of 
potassium makes by far the best solution. It is scarcely 
decomposed by any metal. It may be prepared by digesting 
oxyde of gold in a strong solution of cyanide of potassium, 
but its mode of preparation has been amply detailed when 
treating of the reduction of gold. For our present purpose, 
a strong solution of the salt is to be preferred, and, from 
the corrosive nature of the cyanide of potassium, it should 
always be placed in a glass vessel. For gilding, it would be 
folly, nay, almost madness, to use any other process than the 



ELECTRO-GILDING. 231 

battery, of which the single-battery process will answer 
every purpose where time is not an object, and is indeed as 
a general rule to be much preferred ; but if great speed is 
required, the compound battery made of two, three, or four 
batteries must be employed, or more cyanide of potassium 
must be added to the solution of gold. The size of the 
battery need never exceed the size of the object to be gilded, 
though if it be larger, it will not be of any material con- 
sequence, as a strong obstacle to the passage of the current 
is situated at the positive gold pole. The positive pole, as a 
general rule, should consist of a piece of pure gold flattened, 
and the part exposed to the solution should not exceed the 
size of the object to receive the deposit. 

Every portion of the object on which we are desirous to 
have no layer of gold, must be coated with tallow, wax, or 
any other non-conducting substance, the presence of which 
will prevent any deposit from taking place on those parts. 
In this way, an object may be coated to any desired limit. 
or upon any circumscribed parts of its surface, as, for 
example, drawing or writing thereon. The rapidity of the 
process may be regulated to the greatest nicety by placing 
more or less of the positive plate of gold in the solution, by 
which means, as in other cases, the quantity of electricity 
passing may be regulated with the utmost precision. 

The time occupied for the process must vary according to 
the amount of electricity passing, and the quantity of gold 
required to be deposited; but the thickness of the deposit 
can at any time be learnt, either by ascertaining the ad- 
ditional weight it has received, or by the reduction which 
the positive gold pole has suffered. 

To conduct this elegant process with the greatest economy 
of time, the quantity of electricity should be so regulated to 
the strength of the metallic solution, that the hydrogen is 
kept below its point of evolution from the negative plate ; 
for we must always bear in mind, that the evolution of 



232 SILVER OR COPPER-GILDING. 

hydrogen is attended with evil, as the precipitate will then 
be in one of the finely-divided states, or even as a black 
powder. 

During the process, particularly if the object have a rough 
surface, it is a good plan to remove it from the solution 
before the completion of the process, and rub it with a hard 
brush and a small quantity of whiting or rotten-stone, and 
well wash it ; by these means, any finely-divided metal will 
be removed, and the gold will be precipitated in a very even 
manner. This cleansing is not required when the deposition 
takes place very slowly from the auro-cyanide of potassium. 
The colour of the gold, if the precipitated layer be very thin, 
will be a greenish yellow, but when thicker it will be the 
natural colour of the pure metal. 

The state of the surface of the reduced gold varies with 
the rapidity of the process, in relation to the strength of the 
metallic solution. If reduced very slowly it will assume the 
beautiful frosted appearance of dead gold. If deposited more 
rapidly the surface will have a brighter appearance. If still 
more rapidly the surface will again begin to be brown, and 
quicker than this the operator must not conduct his process ; 
for then the spongy deposit begins, which the electro-gilder 
should shun as the very bane of his art. 

All objects of silver may be readily gilt in this way, and 
objects of copper with as great facility as those of silver. 
Some suppose, and, perhaps, with good truth, that copper 
articles require less gold than silver ones ; the silver when 
heated having the property of taking into itself a certain 
portion of gold. However, copper is more difficult to bring 
into a thoroughly clean state than silver, especially in deep 
crevices. For those cases it is better to plunge the copper 
article into some acid solution of a metal which it can spon- 
taneously reduce; for instance, into dilute sulphuric acid, 
containing a trace of either nitrate of silver, chloride of 
platinum, palladium, or gold, the object of which immersion 



ELECTRO-GILDING. . 233 

is not in any way to leave a deposit of the new metal upon 
it, but thoroughly to cleanse the surface. After this immer- 
sion the object may be washed, and as much of the reduced 
metal as possible rubbed off by means of a hard brush, when 
it will be found to possess a surface admirably adapted for 
the reception of the gold. 

If we have a number of small articles to gild, we may sus- 
pend them in the solution of gold opposite to the positive 
pole ; and especial care must be taken that each part of the 
object is exposed for the same length of time opposite to, 
and at the same distance from, the positive pole; for any 
variation in this respect would cause a different thickness of 
gold to be deposited. The workmen may be well assured, 
that if any article has an unequal coating of gold, it is owing 
either to some of the above causes, or that a different 
relative amount of the positive plate of gold radiated to the 
various parts of the object. 

An imperfect layer of gold betokens imperfection in the 
cleansing of the object before immersion. Electro -gilding is 
applicable from the finest platinum wire, to any object how- 
ever large ; and no doubt the dome of St. Paul's could be 
gilt as readily as a silver thimble, if any person could place 
it in a proper apparatus. 

Whatever be the object to be gilt, it is highly important 
that every part should be entirely immersed in the liquid, or 
else that part at the junction of the air and water might be 
liable to be rapidly dissolved. 

The extent to which gold is applied to silver and copper 
articles is very great, and no variation is required in the 
process, except in those cases where the object itself may 
form a decomposition-trough — as silver vases, the bowls of 
large ladles or spoons, where it is only necessary to fill them 
with the solution of the auro-cyanide, which, in this case, 
should contain no free cyanide of potassium ; connecting 
them by means of a wire with the zinc of a battery, and 

12 



234 STEEL-GILDING, ETC. 

inserting a plate of gold in connection with the silver of the 
battery in the interior of the solution, taking care not to 
allow the gold and vessel to form a metallic contact; but 
even in these cases it is far better to immerse them entirely 
in the liquid for reasons before stated. All these cases of 
gilding appear to be rather for appearance and beauty than 
utility ; but sometimes metals are coated for the protection 
which the coat of gold affords : thus the hair-springs of 
chronometers have lately been gilt by this process, and 
patents have been taken out for its application — a circum- 
stance to be more fully considered when treating of the his- 
tory of electro-metallurgy. The gilding of iron and steel 
only differs from gilding silver and copper in the necessity 
to be careful to overcome the difficulty which occurs in most 
thoroughly cleansing the iron. It should be plunged into 
dilute sulphuric acid, and allowed to remain for a short time 
in that fluid before being immersed in the auro-cyanide ; 
and if we wish most thoroughly to protect the metal from 
the action of extraneous causes, a tolerably thick layer of 
gold should be used. I am informed that the application of 
heat to the auro-cyanide favours the adhesion of the metals. 

Some years ago the attention of engravers and etchers 
was directed to the application of gilt copper-plates for 
their art, instead of plates prepared with the biting ground, 
as now employed ; but a difficulty arose in coating the surface 
so thoroughly as to resist nitric acid in every place, except 
where, by the aid of his etching instrument, he cut through 
the gilt. It is not improbable but that electro-gilding might 
be now employed for this object, and, indeed, I recollect 
seeing the fact mentioned in one of the Journals, but I am 
unaware whether it is at present practically carried into 
effect. 

Cliche es and objects of lead, tin, and pewter, are rather 
difficult to gild in the same way, because their surfaces, 
although scraped very clean, seem to become coated with 



GOLD COLOURING. 235 

an insoluble cyanide which prevents a good cohesion. It 
might, perhaps, be a good plan to coat the surface with the 
slightest layer of copper by immersing it in verdigris dis- 
solved in vini ger. 

The electro-gilder will occasionally find that his salt will 
get into a very inactive state, apparently without any cause. 
The subject is deserving further inquiry, but I would venture 
to assert, from facts that have come to my knowledge, that 
it is owing to the absorption of oxygen, either from the 
atmosphere or at the positive pole of the trough. This 
circumstance, therefore, should at any rate be avoided, by 
leaving the solution when not in use as short a time as 
possible in contact with the air, and by increasing the size of 
the positive gold pole when we desire a large quantity of 
electricity to pass, rather than increase the series of batteries. 
The same observations apply to all the metallo-cyanides, for 
even the yellow ferrocyanate of potash will become partially 
changed into the ferroscsquicyanuret by long exposure of its 
solution to the air. 

After any object is gilt, it is usual to colour it, by which 
much is added to its richness. If we wish simply to give 
the gold a darker colour, the following process is said to be 
well adapted : two ounces of alum, two of saltpetre, and half 
an fcunce of sal enixum are well powdered together, and 
placed in a pipkin w T ith about four or six ounces of water, 
and warmed over a fire ; into this, one ounce of what is 
termed gilders'-wax is placed, which is to be dissolved and 
gently simmered. The mixture must be allowed nearly to 
cool, when the object is to be plunged into it two or three 
times, and then withdrawn ; the oftener the process is 
repeated the deeper the colour of the gold. It is then to be 
well rinsed in cold water and brushed with a nail brush. A 
green colour is said to be given by soft soap and alum. By 
the electric current alone, the colour of the gold may be 
varied considerably by variations in the quantity of electricity 



236 



BURNISHING. 






in relation to the strength of the metallic solution. In fact 
I have observed gold of every colour reduced from the auro- 
cyanide, and even other solutions. 

In many cases the object was soon removed from the 
precipitating trough, has only to be well washed in soap 
and water, when it is quite fit for use ; and in this state 
presents the appearance called dead gold. Sometimes the 
operator is desirous of having his object bright, either en- 
tirely or partially, so that the bright and dead parts may 
form a contrast with each other. In this case the object is 
dipped into a solution of soft soap, to which a 
little prussic acid is added, thoroughly to cleanse ^' 
it, when an instrument called a burnisher (b), 
which is nothing but a bright piece of steel, the 
shape of which is suitable to the object to be bur- 
nished, is rubbed over it two or three times, and 
finally the process is completed by a bloodstone 
(s) fixed upon a handle. The operation of bur 
nishing is generally performed by women ; and it 
is indeed remarkable that they should have learnt 
the use of prussic acid for cleansing gold, which 
has been employed for many years, especially 
when we consider that the fact was not known to chemists at 
the time. It is worthy of remark, that the solution oftsoft 
soap and prussic acid is admirably adapted for cleansing 
trinkets and all articles of gold when they have become 
dirty. 

(197.) The process of gilding by galvanic precipitation 
from a solution of gold, is very different in its effects from 
the method formerly patented by Elkington, termed water- 
gilding ; by the latter process the metal which is to be gilt 
is dissolved in an equivalent proportion to the gold deposited, 
and therefore as soon as a mere surface of gold is obtained, 
it has been supposed that no further deposition can take 
place ; but when the gilding is effected by the galvanic 



WATER-GILDING —MERCURY-GILDING. 237 

battery, any amount of gold may be applied upon the object ; 
a consideration of no small importance, as upon the thickness 
of the coat must depend the durability of the gilding.* 

It is not the solution of nitro-muriate of gold which is 
used for water-gilding, but a solution of the oxide of that 
metal in potash. The solution may be prepared by adding 
caustic potash, or its carbonate, to the ordinary solution of 
gold, in such proportion that the precipitate first formed is 
re-dissolved, when it is fit for use. To gild any article, it is 
plunged, after being first thoroughly cleansed, into the hot 
solution, and allowed to remain in the solution till a thin 
coating is obtained, at the expense of a small quantity of 
silver. 

(198.) There are, besides these processes, other modes of 
gilding used in the arts ; as gilding by amalgamation. In 
this case, a mixture of finely-divided gold and mercury is 
rubbed over the object, and the mercury is afterwards driven 
off by heat. This process is very detrimental to the health 
of the workman, as the fumes of mercury are extremely 
poisonous. It is to be hoped, therefore, that the process of 
gilding by the galvanic current, will, after a period, entirely 
supersede this most injurious operation. 

In gilding very large vessels, the workmen are obliged to 
be extremely cautious not to submit themselves long to the 
action of the fumes ; extraordinary contrivances have been 
used to prevent the inhalations of the metal. The old au- 
thors draw most dismal pictures of the horrors of mercurial 
inhalations, and not without cause, for it is not at all uncom- 
mon for the medical men to witness salivation, universal 
trembling of all the limbs, nervousness, nay, even death 

* Mr. Cooper, however, in an admirable lecture delivered at the Royal 
Institution, stated that this opinion is unfounded, and that any layer of 
gold might be deposited by this process. His assertion shows that this 
mode of gilding must be more or less imperfect, otherwise the copper or 
silver would be prevented, by the coating of gold, from further action. 



238 ELECTRO-PLATINATING. 

itself from this powerful agent. It is a sad matter of noto- 
riety, that as soon as the workman becomes the prey of the 
disease caused by following his business, the master dismisses 
him as an unprofitable servant, and casts him off as worth- 
less dross. 

A comparison between the durability of gilding by the 
galvanic process, with that by the other methods, can only 
be made after the lapse of a considerable period ; I find, 
however, that some spoons and other articles which I gilt by 
the battery, wear extremely well. The thickness of the 
deposit can be regulated with the utmost accuracy, from the 
thinnest possible layer to a coating of an inch in thickness. 

Electro-gilding appears not to be generally applicable for 
non-conducting substances, for I have not at present suc- 
ceeded in applying the gold to any extensive surface, although 
I have seen it grow, for a short distance, over blackleaded 
sealing-wax. Perhaps by using the strongest solution of 
gold, it may be possible to gild surfaces in that way. 

Electro-gilding is generally an advantageous process ; for 
the value of the materials used is trifling. It can be, however, 
repeated at pleasure ; and probably an article could be nearly 
twice as thickly gilt by electro-metallurgy, at the same cost, 
as once by amalgamation, on account of the waste of gold and 
mercury, which always ensues in the latter operation. 

(199.) Platinating metals by the galvanic current, is a new 
feature in science. The process is similar in all respects to 
gilding, but is more difficult. The best solution to be em- 
ployed is the nitro-muriate of platinum, to which sufficient 
soda is added to render it neutral. The object to be coated 
should be smooth, and thoroughly cleansed by potash before 
the process is commenced. Having proceeded thus far, and 
the solution of platinum being ready, a fine platinum wire, 
in connection with the silver of a compound battery, must 
be placed so as to dip into the solution, but must not be im- 
mersed beyond a very short distance. The object to be pla- 

i 



ELECTRO-PLATINIZING. 239 

tinated is now ready for connection with the zinc of the 
battery ; after this is effected, it is to be dipped in the solu- 
tion. {Fig. 23.) Immediately, oxygen gas will be given ofT 
from the platinum wire, in connection with the silver. From 
the copper or other metal to be platinated, no gas will be 
evolved, provided too much electricity be not generated. In 
a few minutes the object will be coated with platinum. 

This process must not be confounded with that by which 
negative metals are prepared for my battery ; for, in this case, 
the platinum is precipitated of the colour and appearance of 
platinum, but in the latter case it is thrown down as a black 
powder. The first process I propose to name platinating in 
contra-distinction to platinizing. To platinize metals, we 
use a strong current to throw down the metal in the black 
powder: to platinate, we may employ solutions of any 
strength, but we must use more moderate currents, so that 
the electricity is insufficient for the production of hydrogen. 

An attempt has lately been made to form my battery of 
platinized lead* as a substitute for platinized silver, but 
with only partial success. Before publishing an account of 
the battery, I tried lead, and even all its alloys, as solder, 
pewter, type-metal, fusible metal, &c, together with most 
other metals and alloys usually met with in commerce, but 
was very ill satisfied with the result ; for many parts of the 
surface soon become imperfect from the deposition of sulphate 
of lead, independently of the imperfectly-conducting nature 
of the lead itself. I tried to obtain lead plated with silver, 
but did not succeed, being informed that the two metals 
would not roll together. Now, however, that we can silver 



* Perhaps platinized lead scarce possesses more than half the effective 
surface that platinized silver does ; but it is a fact very difficult to ascer- 
tain, being the (I A) of my equation, which is by no means equal to the 
work performed when the battery is connected with a voltameter, because 



240 ELECTRO-PLATINATING. 

lead by voltaic electricity, it perhaps might be employed ; or 
we may palladiate the metal by simply immersing it in a 
dilute solution of the nitrate of palladium, and then platinize 
it. Upon the whole, perhaps, platinized lead is better dis- 
carded, unless silvered or palladiated, especially as we can 
always make a cheap battery of platinized iron if we want a 
battery of large surface to last a short period, and platinized 
plumbago, charcoal, or even cinders are preferable to pla- 
tinized lead. To sum up in a few words my experience in 
the construction of the battery : — it is preferable that the 
finely-divided metal should be either platinum, palladium, or 
iridium, the first being best ; and the metal to receive the 
deposit platinum, palladium, gold, silver, carbon, or iron, 
which are preferable ; then follow tin, lead, and their several 
alloys, together with those of antimony and bismuth ; whilst 
zinc, cadmium, copper, are the worst of all the metals. 

A cheap metal or alloy for the reception of the finely 
divided metals, that would not undergo the slightest change 
in dilute sulphuric acid, would be hailed by electro-metallur- 
gists as a great boon ; perhaps some compounds of silver, 
zinc, and nickel might be discovered applicable for this 
purpose. 

Specimens of electro-platinating which I have prepared 
by this method, will not resist the action of nitric acid, be- 
cause there are generally some little fissures uncovered, some 
little crack which, admitting the nitric acid, tears off the pla- 
tinum in thin scales. It is not applicable to rough surfaces, 
as it is preferable that the surface for its reception should 
be smooth. The colour of the metal thus reduced is so 
similar to polished steel, that it would be difficult to distin- 
guish the one from the other. It is needless to say that it 
has a beautiful appearance. It would be of great value as a 
coating for telescopes, microscopes, quadrants, and a hun- 
dred other articles which must be exposed to the action of 
the weather. 



ELECTRO-SILVER PLATING. 241 

(200.) To palladiate articles, we adopt methods similar in 
all respects to those used in platinating them. We employ 
the ammonio-muriate of palladium dissolved in liquid am- 
monia, and employ the compound battery process with a 
small positive platinum pole. The palladio-cyanide of po- 
tassium with a palladium pole may also be employed. This 
metal is whiter than platinum, but not so bright as silver. 
It may be used in the same cases, and with the same ad- 
vantages, as platinum ; and we have, besides, twice the bulk 
of metal in the same weight. 

Palladium adheres with such firmness to copper, when 
reduced by voltaic electricity, that it is almost impossible to 
remove it when once deposited. It might be worth while 
for experimenters to ascertain how far it mighty be employed 
for the protection of iron or steel. 

(201.) There is no process at the present time more 
readily conducted than electro-silver plating. The best 
solution which can be used is the argento-cyanide of potas- 
sium. It is generally made by boiling the oxyde of silver 
in a strong solution of cyanuret of potassium. The process 
which is most favourable is the single battery. The solu- 
tion should be placed in a glass vessel, and used with a 
silver positive pole, about the same size as the object to be 
silvered. The same precautions should be taken, and the 
same measures observed with regard to plating as gilding. 
The object should be clean, in order that a most perfect 
adhesion may be effected between the object to be silvered 
and the reduced metal. The silver will be thrown down in 
somewhat different states, according to circumstances. If 
thrown down very slowly, it will assume a beautiful dead 
appearance ; if still more rapidly, it will be brighter. It is, 
perhaps, as well to use the solution as strong as possible, 
and take care to stir the liquid occasionally, in order that a 
proper diffusion of the metallic salt may take place. As a 
precipitating trough, either the vertical or horizontal may be 



242 ELECTRO-SILVER PLATING. 

employed according to circumstances ; the latter is to be 
preferred for large, surfaces, as waiters, and similar objects ; 
in which case a corresponding large plate of silver should be 
used as the positive pole, and placed over the object to be 
silvered. Sometimes a large circular silver positive pole 
may be made to surround the object. The silver positive 
pole is to be connected with the silver plate of a battery, 
exposing nearly as much surface as the object to be plated, 
whilst the object to be plated is to be connected with the 
zinc. A little free cyanuret of potassium, added to the 
argento-cyanide of potassium, hastens the process by in- 
creasing the solubility of the positive pole. The quantity of 
metal reduced can be readily ascertained, either by finding 
the additional weight of the object receiving the deposited 
silver, or by ascertaining the deficiency of the positive pole. 

At the present time all electro-silver platers take advan- 
tage of the peculiar qualities of bisulphuret of carbon, for 
causing the metal to be deposited quite bright, as described 
when treating of the reduction of silver ; and so perfect is 
the method now adopted, that they are enabled to perfect 
articles for sale, without polishing, scratch-brushing, or other 
operation. 

Electro-plating is now most extensively carried out, not 
only for every legitimate kind of business to which plating 
can be possibly applied, but also, I regret to state, for the 
bad purposes of false coining. The forgers purchase the 
Britannia metal spoons and melt them to form afac simile of 
the coin. But the greasy feeling of lead would lead to instant 
detection, and hence they cover the surface with a very thin 
film of silver. The cheat may be detected by the coin bejng 
about one third lighter; also, on being rubbed between the 
fingers, they give off the peculiar smell of the cyanide of 
potassium, and if touched with a drop of strong nitric acid, 
the silver comes off, and a black mark is produced. A vast 
number of these coins are in circulation, made so well that 



ELECTRO-SILVER PLATING. 243 

ringing as perfectly as the ill-struck coins of the Mint, they 
may readily deceive the casual observer. The coiners are 
continually convicted and transported, but new ones arise 
to carry on the illegal process. If these men would but 
make medals by the same process, to sell at a cheap rate, 
they would earn good wages, and be valuable members of 
society. 

Plated articles may be either partially or entirely bur- 
nished in the same way as gilt objects, according to the 
fancy of the operator ; and the contrast of dead silver with 
the bright polished metal much increases the beauty of the 
object. 

Copper and its alloy are most readily silvered by this 
process, but lead does not take the metal so freely ; it does 
indeed become coated, but the two metals have not generally 
a firm adhesion, because the lead, although made perfectly 
clean, becomes in part coated with an insoluble cyanide 
immediately it is immersed in the solution. Perhaps the 
best mode of remedying that would be to reduce a thin film 
of copper upon the object by immersing it in verdigris dis- 
solved in vinegar, or by touching it with a solution of the 
nitrate of palladium, by which a slight film of metal would 
be reduced. 

Non-conducting substances can be silvered by first black- 
leading them, then attaching a wire in such a way as to 
come in contact with the plumbago. In this case we should 
be careful to use rather a larger plate of silver than the 
object, as that favours the growth of the metal, but as a 
general rule it would be preferable to coat the object first 
with copper and then silver it. 

(202.) The mode in which articles are plated indepen- 
dently of electro-metallurgy, is very different from the one 
now used. It is customary to take an alloy of silver and 
copper, about the standard used for coining, and to solder it 
on a bar of copper. This bar is then rolled out thin, by 



244 ELECTRO-SILVER PLATING. 

which means, as the two metals extend equally, the silver 
forms an exceedingly thin covering. This plated metal is 
then, by hammering, formed into the required shape, and 
soldered to other parts. The handles and edges are made 
of thin silver rolled to about a square foot to the ounce, 
which is first embossed with a die, and then the hollow parts 
are filled up with solder. These steel dies at some manu- 
factories have cost alone many thousand pounds. Now, 
although the silver on plated articles is so exceedingly thin, 
it is astonishing, if the goods are well made y as Sheffield 
goods usually are, how long the thin coat lasts. This excel- 
lent result is owing to the compression and hardening that 
the metal undergoes during the process of rolling. In this 
respect it is superior to electro-plating, but the process can 
never be repeated, whilst electro-plating may be performed 
any number of times. 

Electro-plating is of considerable advantage to the ope- 
rator, for articles may be made entirely of copper, and even 
finished with laborious minuteness, and then silvered. The 
probability is, however, that electro-plated articles will not 
wear quite so well, in proportion to the thickness of the 
metal, as ordinary plating, for all metals reduced by elec- 
tricity are found not to resist attrition so well as rolled 
metals. Electro-silver plating is a cheap process, indepen- 
dently of the intrinsic value of the silver used. Electro- 
silver plating is now most extensively employed to cover 
spoons and various other objects, even such as formerly I 
should hardly have considered adapted to be the subjects 
of the process ; and it now forms an important branch of 
manufacture. 

(203.) Metals may be covered with nickel, by proceeding 
as in the former cases. The solution to be used is the 
chloride of nickel, with a nickel positive pole. The single* 
battery process is to be preferred, but pure nickel, thpugh 
very brilliant, is apt to be rather brittle. 



ELECTRO-COPPERING. 245 

t04.) Various substances, both metallic and non -metallic, 
may be coated with copper by the agency of the galvanic 
current. The various solutions to be employed, and the 
apparatus to be used, have been already fully described, 
when treating respectively of electro-metallurgic apparatus, 
and the reduction of copper. As a general rule, the single 
battery apparatus is to be preferred, and an acidulated 
solution of sulphate of copper, as the salt from whence the 
reduction of copper should be effected. The solution given 
before is well adapted for a smooth deposition of metal, 
but it must contain more metallic salt when we desire the 
crystalline deposits. The advantage of its application relates 
principally to non metallic substances, which may, in this 
way, receive a metallic surface of pure copper, Not the 
slightest difficulty would attend the coppering of almost 
any metal ;. and it is a process which is frequently used in 
the arts. 

(205.) Coppering non-conducting substances may be 
divided into two departments ; the first of which contains 
those which require the deposit to assume, as nearly as 
possible, the form of the original substance ; the second 
comprises those cases where the deposit is desired to be in 
a crystalline state. 

A somewhat different arrangement is required in each 
instance ; for in the first, the battery and solution must be 
so arranged that the hydrogen is near the point of evolution ; 
but in the second, the solution may be much stronger, and 
the quantity of electricity may be increased by increasing 
the size of the battery, and the surface of the positive copper 
pole in the decomposition apparatus. 

(206.) In the first division we have delicate substances, 
such as medallions, &c. The substances of which the cast 
is made should be rendered most thoroughly non-absorbent 
by the processes already described. For this purpose the 
medal must be boiled for such a time in wax, stearine, sper- 



246 



ELECTRO-COPPERING. 



maceti, or tallow, till it becomes translucent, or semi-trans- 
parent. It is then to be brushed over with black-lead, and 
at the edge a very fine copper wire is to be once twisted, in 
order that perfect contact may exist between the battery 
and black-lead. It is now ready to be placed in the solution 
of acidulated sulphate of copper, the end of the wire having 
been first connected with the zinc of the battery. After this 
has been done, the last thing is to place a piece of waste 
copper in the solution, rather larger than the cast, and to 
connect it, by means of a wire, with the silver of the battery. 
Action will immediately take place, the copper will be dis- 
solved, and the metal precipitated on the black-lead of the 
object, spreading over the surface till the whole is covered. 
It is as well, perhaps, to use a large positive pole of copper 
and a small battery, so that the decomposition may take 
place very slowly, which causes the surface to assume a 
delicate matted appearance. In some cases we may use two 
batteries arranged as a series for this purpose, as that will 
ensure more rapidly the uniform spreading of the copper 
over the medal. The medal must not be left in long after 
it has been coated, as that will detract much from its sharp- 
ness and beauty ; after it has been taken out, it may be 
rubbed over with coarse paper to remove any little asperity 
that the copper may have thrown up. To the numismatist 
this process will appear barbaric, as he would consider that 
it would detract from the beauty of the medal ; but though 
decidedly detrimental, it is not so injurious as might at first 
sight appear ; because as the copper is of nearly uniform 
thickness all over, the effect is to increase in size the whole 
design. By the sculptor and architect, perhaps, it might be 
used with advantage to coat statues or other ornaments. In 
all these cases it is advisable to coat not only the front but 
the back of the object with the metal. 

Small statuettes of plaster or wax are now frequently 
covered with copper, and are nearlv as beautiful as bronze. 



ELECTRO-COPPERED FRUIT, &C. 247 

In these cases the whole success of the process depends upon 
so thoroughly boiling the plaster of Paris cast, that it shall 
totally lose its power of absorbing water, or otherwise some 
of the metallic solution will enter into its pores, and in 
process of time will surely crystallise and thrust off the coat- 
ing of copper. Many of the most lovely electro-coppered 
medallions which I formerly made »are now totally destroyed 
from this cause. 

At the present time gutta percha has come to our aid, 
and already electro-coppered gutta percha inkstands and other 
articles are sold. This alone opens a wide field of extend- 
ing art into the ordinary manufactures ; and the time must 
come when the manufacturer will only succeed when he 
adds the taste of the artist to the knowledge of the chemist. 
Chemists occasionally protect their retorts and glass vessels 
by covering them with copper. For this purpose the glass 
is varnished and covered with gold leaf or plumbago. This 
vessel is then attached, by a wire, to the zinc of my battery, 
and a large positive pole surrounds the object to be coated. 
This positive pole is converted to the platinized silver, when, 
after a certain time, a sufficient deposit ensues. 

(207.) A pretty application of the art of coppering is 
suitable to horticulturists, as by its means, fruit, vegetables, 
leaves, seeds, and various other specimens may be coated 
with copper, either for ornament, or for the purpose of 
illustrating the size, form, and other peculiarities of the object. 
Apples and pears may be very readily coppered ; they are 
to be brushed over with black lead, and then a small pin is 
to be thrust in at the stalk ; to this a wire should be attached 
which is connected with the zinc of the battery. It may 
then be placed in the solution, and the whole arrangement 
completed by the insertion of a piece of copper, which is to 
be connected with the silver of the battery. In a similar 
manner, cucumbers, gourds, potatoes, carrots, and a hundred 
other vegetable seeds and roots can be covered. The wood- 



24S 



ELECTRO-COPPERED LEAVES, 



Fig. 36. 




cut exhibits a bunch of Portugal grapes 
submitted to the action of the fluid to be 
electro-coppered. The form, after the pro- 
cess, is characteristic, and marks so strongly 
the individual character of each variety, 
that the horticulturist is at no loss to dis- 
tinguish the specimens at once. The con- 
dition in which the copper is thrown down, 
can of course be varied according to the 
laws set forth in the last chapter. For or- 
namental purposes, the crystalline copper is the most beauti- 
ful ; but for a specimen intended to illustrate the form of the 
object, the smooth copper is best adapted. After the objects 
are completely covered, the pin is to be withdrawn, which 
will leave a little hole, and that enables the evaporating juices 
of the vegetable to pass freely out, and thus promotes the 
complete drying of the encased object. A cucumber which I 
coated during the past summer, appears now to contain 
scarcely anything inside the copper, and the pears, apples, 
&c, consist of little else but the metallic coat. The botanist 
will readily perceive in what way this process may be em- 
ployed for his advantage. 

The beauty of electro-coppered leaves, branches, and 
similar objects, is surprising. I have a case of these speci- 
mens placed on a black ground, which no one would take to 
be productions of art. In the same room with them are a 
couple of those cases, in which Ward has taught us to grow 
in this smoky metropolis some of the most interesting 
botanical specimens. In these cases are contained varieties 
of fairy-formed adiantums, verdant lycopodiums, brilliant 
orchideas, rigid cacti, and creeping lygodiums, all growing in 
their natural luxuriance. The electro-coppered leaves, how- 
ever, are beautiful when placed by the side of the productions 
of this miniature paradise ; and when I state that the nume- 
rous hairs covering the leaves of a melostoma, and even the 



ELECTRO COPPERED BASKETS. 249 

delicate hairs of the salvia are all perfectly covered, the 
botanist must at once admit that these specimens have rather 
the minuteness of nature than the imperfections of art. 

(208.) A beautiful effect of metallic surfaces may be ob- 
tained by the deposition of crystallised metal on baskets. The 
wicker-work must be black-leaded, and connected by means 
of a wire to the zinc of a galvanic battery ; when on being 
immersed in the metallic solution, and the circuit completed, 
it will be covered with the most beautiful crystals of copper, 
sparkling in the light from the facets of thousands of little 
crystals. It is as well to pass a very fine copper wire round 
several parts of the basket, so that it may touch the black- 
lead in several places, for this will insure the coating being 
more rapidly complete. Any other mode of giving a con- 
ducting surface will answer equally as well as black-lead. 
The copper pole for these objects should be very large, and a 
series of two or three batteries employed. The solution of 
sulphate of copper should be perfectly concentrated, for all 
these circumstances will tend to render the copper crystalline. 
Baskets thus prepared, and filled with metallic fruit, leaves, 
insects, &c, might be used as ornaments for the drawing- 
room, and would greatly exceed in interest the usual append- 
ages ; for if these objects were made by the individual who 
possessed them, it would show his interest in the noble science 
of galvanism ; and if they were purchased, it would be the 
means of encouraging the application of this powerful agent 
to the arts and manufactures. It is now, indeed, but a small 
germ, but will doubtless become a vast tree, which by bearing 
fruit will cause a mighty revolution in many manufactures. 
£et the attention of the wealthy be directed to the subject ; 
let them patronise ornaments made by these means, and then 
speedily will the artizan become more perfect in his work, 
and the galvanic fluid will be as commonly used as steam or 
gas. I particularly dwell upon these circumstances in this 
place, because most coppered objects are exceedingly beau- 



250 ELECTRO-COPPERED SHIPS. 

tiful, and many of them could not possibly have been made 
by any other process heretofore known. 

In fact there is nothing, organic or inorganic, which will 
remain in a solution of salt of copper a few hours, that may 
not be coated with the metals. 

The foregoing electro-coppered objects are trifling com- 
pared to the purposes to which electro coppering has been 
tried; for actually, experiments have been made to cover the 
bottoms of ships with that metal. There are two or three 
experimenters who lay claim to the first idea of the inven- 
tion; one of them is Mr. Hays, a distinguished practical 
chemist of Portsmouth, and experiments have been tried at 
the dock-yard at Portsmouth upon the subject ; Mr. Hays 
first coats the bottom of the vessel with pitch, thoroughly 
black-leads it, and then attaches wires as a medium of com- 
munication with the plumbago, and the zinc of a very large 
battery. The vessel is laden with ballast till it sinks as low 
in the solution of acidulated sulphate of copper as it is desir- 
able that the copper should extend. The solution of the 
metallic salt is placed in a suitable reservoir, and a large 
positive pole, composed of sheets of copper, is attached to the 
silver of the battery, which completes the arrangements. In 
this mode of proceeding the negative pole being above the 
positive, a proper diffusion of the newly-formed metallic salt 
cannot take place as readily as could be desired, and it would 
be attended with much trouble to turn the boat over, so that 
the positive pole might be arranged over the bottom of the 
boat ; especially, if it were a first-rate man of war. In all 
large commercial operations, the expense becomes the most 
important consideration, and I am afraid that in this case, 
the cost of the reduction of copper when added to the labour 
required for the process, will not at all compensate for the 
additional time that the reduced copper would last over the 
copper sheathing as usually employed. 

(209.) Earthenware, or any other similar substance, can be 



ELECTRO-TINNING, ZINCING, ETC. 251 

coated in like manner with the metallic copper; but when 
these smooth surfaces are to be covered, some difficulty 
arises, which may be overcome by the previous application 
of a very little varnish. In this way, by coating a jar or 
gutta percha cell with copper, copper batteries are frequently 
made. 

Electro-coppered objects may be gilt, silvered, or coated 
with other metals. Crystalline objects, however, are more 
beautiful in their cupreous character ; though smooth ob- 
jects, as leaves and fruit, are very beautiful when gilt. 
Electro-coppered objects, when silvered, are not so striking 
as either of the other two, and this on account of the dull 
whiteness of the silver. 

(210.) Metals may be coated with nearly every other 
metal besides those I have so fully described. Some of these 
metals are found to be much more troublesome than others, 
and some will only give an irregular coating ; yet, by fol- 
lowing the principles explained in a former book, any metal 
may be thrown down in the reguline state, with more or less 
success. 

(211.) Electro- tinning is a process which, whether con- 
sidered in its difficulty, inefficiency, inutility, or expense, is 
equally disadvantageous. To obtain a thick layer of tin 
directly by electricity, would be extremely difficult ; and al- 
though a thick layer may be readily obtained by depositing 
either crystalline or spongy tin, and then fusing it, I cannot 
see that any advantage is likely to accrue from such a pro- 
ceeding. Perhaps the sulphate of tin is the best solution 
that can be used for this purpose, conjoined with the single 
battery process. 

Electro-leading is a process equally unfavourable in its 
results, as electro-tinning. The tris-nitrate of lead makes 
perhaps as good a solution as can be employed for this 
purpose. 

Electro-zincing is not attended with any great difficulty ; 



252 ELECTRO-IRONING, ETC. 

the metal may be readily reduced from the sulphate, made 
as neutral as possible. The single battery apparatus should 
be employed with a zinc positive pole ; any metal may be 
used to receive the deposit, taking care to employ it very 
clean, and the smoother it is, the more favourable will be 
the result. 

Metals may be readily coated with a beautiful deposit of 
iron, by using the proto-sulphate, or neutral chloride of iron. 
The single battery process with an iron positive pole is best 
adapted for this object. 

The facts in this book are generally new, and their appli- 
cation is extremely interesting ; for to those who follow gal- 
vanic science as an amusement, the exercise of the arts of 
gilding, plating, and coppering, will not only be interesting 
but useful ; in the arts doubtless they will assume a higher 
importance, and add new branches for the successful appli- 
cation of electricity. Those who are desirous of following 
these processes as a business, will find that practice alone 
will make them perfect ; and as the scientific man details the 
principles to be pursued, so the mechanic must follow these 
laws, and regulate the details as his extended experience 
may dictate. 



253 



BOOK THE FOURTH. 

ON VARIOUS APPLICATIONS OF THE REDUCTION OF 
METALS BY GALVANISM. 

CHAPTER L 

ON THE MULTIPLICATION OF COINS AND MEDALS. 

Value of Electro-Metallurgy for the numismatist, 212. Mode of obtain- 
ing the mould, 213. Directly by the voltaic current, 214. By lead, 
fusible metal, &c, 215. By non-conductmg substances, 216. Metallic 
duplicates of gold, 217. Silver medals, 218. Medals of platinum, 219. 
Copper medals. 220. Precautions to be taken to prevent air-bubbles, 
221. Apparatus to be employed, 222. Single-cell apparatus, 223. 
Thickness of the metal, 224. Removal of the cast from the mould, 225. 
Zinc medals, iron medals, 226. Value of Electro-Metallurgy for me- 
dalists, 22 7. On the modes of making perfect medals, 228. 

(212.) To the numismatist, the reduction of the metals by 
galvanism is of the highest importance ; for, on the one hand, 
it presents him with the means of having casts of coins, or 
medals, which on account of their great rarity he could 
never otherwise possess, and, on the other hand, it offers to 
the coin-manufacturer the means of forging the more scarce 
coins, so that the collector must be doubly careful in making 
his purchases. At present, I am afraid that our art, in 
unskilful hands, has been the means of destroying so many 
medals, that no benefit which has yet accrued has been able to 
compensate for their loss. 

(2L3.) There are three methods of taking the duplicate of 
a coin or medal. By the first, a primary cast or an intaglio 



254 



MODE OF TAKING THE MOULDS. 



is made in metal, directly by the galvanic precipitation ; by 
the second, a metallic cast of the medal is first obtained, 
either in fusible type, or analogous metals ; and by the third, 
we make the intaglio cast in some non-conducting substance, 
as white wax, sealing-wax, &c. 

(214.) To take a primary cast at once from the medal or 
coin should not be attempted by an inexperienced hand, and 
never by any one from an unique specimen for fear of any 
mischance. The process, however, is simple, and very valu- 
able, when we desire an absolutely perfect intaglio impression 
of any coin or medal. The object to be copied is to be coated, 
on the side where we do not require action to take place, 
with grease, wax, varnish, or other non-conducting substance. 
A fine wire is to be passed around the rim, and then it is 
ready to be placed in the metallic solution. The adhesion 
of the air to the metal is of considerable importance in this 
case, and the metal should not be allowed to remain a 
single instant in the solution before the galvanic circuit is 
completed. 

The obverse and reverse can be copied by two operations, 
or even both by one, taking care to grease the rim, so that 
the whole medal may not be confined by the new deposit. 
This operation gives us two moulds, one of either side of the 
coin or medal, in intaglio. By this process a copper medal 
or coin is liable to have its bronze removed, and, perhaps, it 
is a good plan always to remove the bronze of the medal 
before immersion, by cleansing it with oil of turpentine ; but 
a gold or silver one will not suffer the slightest injury. This 
mould maybe used for making plaster-casts, sealing-wax 
impressions, or it may itself be again used as a mould to 
receive the galvanic precipitate, and we may thus obtain a 
very perfect relievo copy of the original. 

(215.) Intaglios may be taken off coins or medals in lead, 
pewter, fusible metal, tin foil, or silver-leaf, in the manner 
pointed out in the preceding books, and these intaglios are 



MOULDS FOR COINS. 255 

then to have a wire either soldered or placed in connection 
with them, when they will be ready for the reception of the 
metallic precipitation. (134, 135.) 

(216.) The third method, however, is the one which should 
generally be adopted ; for by non-conducting substances we 
can obtain most excellent moulds for receiving the precipi- 
tation. For coins, very small medals, and cameos, impres- 
sions in good sealing-wax are to be preferred by the amateur, 
(130.) These must have a fine wire melted into the wax, 
and be black-leaded, and then they are ready to be copied. 
(144.) At the present time on gutta percha we most chiefly 
place reliance, as for all these purposes its properties are 
invaluable. 

Larger medals may be copied in wax, stearine, bees'-wax, 
and rosin, or plaster of Paris. The plaster of Paris must be 
rendered non-absorbent by any of the processes given in a 
former book ; tallow or spermaceti are best adapted, and 
from their being always at hand, are to be preferred ; they 
are then to be black-leaded, when they may be placed in the 
solution. By either mode, perfectly sharp medals may be 
taken. To the workman who requires to make a large 
number of metallic impressions of coins, I would recommend 
the use of a square piece of plaster or gutta percha of any 
convenient size, say six inches each way, with impressions 
of medals as thick as he can put them. This might be 
easily managed by joining separate plaster moulds together 
till the size is obtained ; this piece must be filled by the 
processes given before, black-leaded, and lastly, the metal 
is to be thrown down upon it. By this means he will obtain 
a sheet of coins, which he may either retain in that form, or 
by cutting them out may have each separately. The copper 
thrown down upon plaster or gutta percha is quite as perfect 
as the original cast. 

(217.) Having determined upon the process to be adopted, 
the operator has next to decide of what metal he will make 






256 SILVER ELECTRO-MEDALLIONS. 






his duplicate. To make a gold medal, perhaps the best 
solution on the whole would be the auro-cyanide ; because it 
allows the use of a great many kinds of metals as the negative 
pole. The modus operandi is similar in all respects to that 
of gilding ; the only difference would be, that the deposit 
should be allowed to be a great deal thicker. I am doubtful 
whether non-conducting substances could be employed in 
this way. 

A very useful mode of the application of gold would be, 
first, to throw down only a moderately thick layer, and then 
to fill up the deficiency by throwing down copper upon it. 
This, to the false coiner, might form a valuable piece of 
information ; but is here mentioned to put people on their 
guard. 

(218.) Silver electro-medallions require a more attentive 
description than gold ones, because the silver is of less 
value, and the process is easy to conduct. Silver electro- 
medallions may be made from every variety of mould — 
metallic (even iron) and non-metallic — that can be employed 
for electro-metallurgy generally. 

For all metallic moulds but little difficulty occurs, except 
that adhesion must carefully be prevented. There is but 
little fear of adhesion of the new metal to iron, steel, or 
lead ; but to copper, silver, and some other metals, there is 
some risk, from the corrosive nature of the solution of 
silver ; perhaps an infinitesimal layer of some greasy com- 
pound might with advantage be employed over the mould : 
that is, the smallest quantity of that substance might be 
rubbed over the mould, and then rubbed over as far as 
possible. The best solution of silver for these purposes is 
a strong solution of the argento-cyanide, though I have 
made medals from several other solutions. The single 
battery process is the best adapted, conjoined with a silver 
positive pole about twice the size of the object to be copied. 

Moulds made of non-conducting substances are also well 



SILVER ELECTRO-MEDALLIONS. 25? 

adapted for the formation of silver electro-medallions. The 
object has only to be black-leaded and connected by a wire 
to a battery about its own size, when the silver will gradually 
grow over the object, cover it, and become of any thickness 
the operator may require. 

The quality of the metal thus reduced, if thrown down in 
the best reguline state, is very strong and elastic ; so much 
so that but a thin deposit will suffice. Sometimes we are 
desirous of having the medal somewhat thicker, which may 
be accomplished in some cases (where we are desirous of 
being economical with our silver), by giving it a layer of 
copper at its back ; the only circumstance of which we have 
to be careful is, to cause a proper adhesion between the two 
metals by making the surface of the silver chemically clean 
before immersion. 

Silver medals are made as readily as copper ones, the only 
extra difficulty being first to get the pure silver ; for every 
electro-metallurgist will not like to pay six shillings an ounce 
for this substance to make medals, independently of the cost 
of the mould and galvanic power derived from the battery ; 
the latter, however, in this case, would not amount to a penny 
an ounce. 

The surface of the silver is quite bright when it is removed 
from bright moulds ; when removed from non-metallic 
moulds it is apt to be discoloured with plumbago : in which 
case the surface should be rubbed with emery or fine char- 
coal powder and a hard brush, and finally polished with a soft 
brush and rouge. 

(219.) Medals may be made with great difficulty of 
platinum or palladium entirely, as in the cases just men- 
tioned : or a duplicate cast of the medals may have an 
exterior of either of these metals, whilst the interior 
may consist of copper. The mould for these metals should 
consist of either gold, platinum, palladium, or silver. The 
solutions may be of any strength, although the operator will 

13 



258 



COPPER ELECTRO-MEDALLIONS, 



find the strongest the best adapted. See the general remarks 
on platinum, palladium, &c. (169 — 171.) 

(220.) Copper is the metal of most importance to numis- 
matists, and it will answer like silver both for metallic and 
non-metallic surfaces. The salt which may be employed for 
ordinary purposes is the sulphate ; and when used for this 
purpose the solution should be more concentrated than when 
the reduced metal is required for the electrotype. A satu- 
rated solution of sulphate of copper, mixed with one-third of 
its measure of dilute sulphuric acid, will answer admirably for 
general purposes. • 

(221.) In making electro-medallions, we must be cautious 
that no bubbles of air adhere to the mould, or are carried 
down into the solution when the mould is immersed. This is 
very apt to occur when the mould is very deep, as sometimes 
a series of air-bubbles may be observed adhering in the hair, 
the beard, or even the top of the nose ; a circumstance which 
would not a little impair the features of the copy. To 
prevent any occurrence of this nature, the medal should be 
inspected after it has been in the solution a short time, 
and any bubble dispersed. If this be not attended to, the 
bubbles would become quite encased with copper, and a little 
hole be left. 

(222.) The battery process is without doubt the best for 
making medals, especially if large ; but the form of the pre- 
cipitating trough must vary according to the size and form 
of the medals to be made. For very large medals, say six 
inches in diameter, a common earthenware basin is the best. 
The medal is to be connected with a wire, and placed flat at 
the bottom of the vessel, and this wire is to be connected 
with the zinc of the battery. A piece of copper is now to 
be procured, which must be somewhat larger than the 
medal above which it is to be placed in the basin. The pe- 
culiar form of the basin will of course prevent the copper 
from descending upon the medal, a result which is carefully 



■ 



VARIOUS PROCESSES. 259 

to be avoided. This copper is to be connected with the 
silver of the battery. The solution is then to be poured into 
the basin, when action will immediately commence ; the 
copper will be reduced upon the mould from the solution, 
and copper will be dissolved from the positive pole to keep 
up the saturation of the fluid. It is always necessary to 
employ a battery sufficiently large ; twice the surface of 
negative metal is most favourable for precipitation, though 
by following the principles already given, any sized battery 
may be employed. For many metals the battery process is 
greatly to be preferred. In this case the vertical precipi- 
tating trough may be used. A piece of copper, connected 
with the silver of the battery, is placed in the middle of the 
trough ; and on either side, as many medals may be sus- 
pended as can be arranged opposite the copper ; and these 
are all to be connected with the zinc of the battery. The 
advantage of this mode of proceeding above all others, is 
the facility given to the operator, either to remove or add 
one or more medals without any injury to the others ; and 
eight, ten, twelve, twenty, or even a million, if he pleases, 
may be made at once. 

(223.) Although the battery process is generally to be 
preferred, yet it does not follow that it is the only mode 
capable of being adopted. Electro-coins and medallions may 
be made by any process described in the first chapter of the 
second book ; as the zinc single-cell apparatus, the iron 
single-cell, the tin or lead single-cell apparatus will answer 
for this purpose, and if the objects happen not to be very 
large, the operator will not find it material what process he 
adopts. The only general rule to be followed, in any case, 
is to take care that the sulphate of copper be concentrated, 
the positive metal sufficiently large, and the distance of the 
positive metal from the mould not too great. A little acid 
added to the sulphate of copper, will generally improve the 
quality of the reduced metal. (107 — 113.) 



260 REMOVAL OF THE MEDAL. 

(224.) By any of these processes we can obtain a perfect 
cast from our mould; yet if the device on the mould be very 
deep, the deposit will not always take place favourably on 
the deepest parts. In these cases, when the medal is nearly 
completed we may remove it from the solution, wipe it dry, 
and .coat the parts most thickly covered with any non-con- 
ducting substance. The medal is then again to be placed in 
the solution, when the deficiencies will be soon filled up. 

Great thickness of copper is not required for medals ; for 
if it be as thick as a wafer, and of good quality, it will amply 
suffice. For most purposes it is of no advantage to have it 
thicker, and when we are desirous of strengthening the 
deposit, the back may be coated with sealing-wax. All these 
details must be regulated by the fancy of the operator, but 
by proper management the deposit obtained in twenty-four 
hours is quite sufficient for many purposes. 

(225.) The last operation is the removal of the cast from 
the mould, which is attended with no great difficulty. We 
must be careful to remove any copper which embraces the 
mould at the edges, by placing the medal and mould in a vice, 
for which purpose a common wooden one answers admirably ; 
then by filing the surplus metal from the edges, and pulling 
one from the other with moderate force, a separation will be 
effected. When the duplicate has taken plkce upon the 
original medal itself, the adhesion will be very slight if the 
precautions are taken which I have before detailed. Casts 
made from most non-conducting substances come off some- 
times so readily that the mould is not the least injured. The 
adhesion, indeed, is greater when leaden moulds are used, yet, 
with care, the duplicate may be removed without much 
detriment to the mould, although it is generally slightly 
impaired. In every case some judgment is required to 
regulate the direction in which we make the pulling force, 
according to the manner in which the prominent parts are 
arranged: for generally there is one way where the cast can 






ZINC AND IRON ELECTRO-MEDALLIONS. 261 

be removed more easily than any other. To copper, &c, 
there need be no adhesion. (125.) 

(226.) Copper electro-medallions may be gilt, plated, pla- 
tinized, or coated with other metals, so that they may exactly 
resemble the original. The coating of foreign metal in this 
case ought to be very thin for fear of injuring the sharpness 
of the cast. * 

Electro-medallions may be readily made of zinc, by using 
a solution of sulphate of zinc, as neutral as possible, with a 
zinc positive pole, and connected with a battery of about the 
same size. Zinc electro-medallions possess no peculiar beauty. 
A metallic mould appears to be necessary in this case. 

Electro-medallions might be formed of iron, by using a 
solution of chloride of iron, an iron positive pole,, and a bat- 
tery about the size of the negative metal. 

Before we can understand the value of electro-metallurgy 
to the medallist, we must consider the processes he now uses 
to effect his object. Medals divide themselves naturally into 
two great classes : the first, which are cast and chased, that 
is, touched up afterwards, and the second division, which are 
made by a piece of metal being impressed with a steel die by 
a heavy blow given by an apparatus called a coining-press. 

The first division of medals are first modelled in wax by 
the artist, from that wax impression a mould is made, and 
from that mould a cast in metal is procured. This cast is 
then touched up by the artist ; but, as each individual medal 
has to be touched up, absolute identity is destroyed. 

For this class of medals electro-metallurgy will undoubt- 
edly supersede the old method ; for the artist may take a 
plaster-cast from his original design, and make by electro- 
metallurgy a perfect fac-simile. The metal-cast he may then 
touch up and bring to great perfection ; and he will be 
enabled to obtain any number perfectly identical with the 
first which he has so laboriously perfected. 

The second division of medals are those coined or made 



262 VALUE OF ELECTRO-METALLURGY TO THE MEDALLIST. 

with a punch. The mode of proceeding in this case is more 
complex ; but let us trace the processes necessary to make 
the current coin. In the first place a likeness of the reigning 
sovereign is modelled by the artist in wax, which being ap- 
proved of is finished as highly as possible in that material. 
The coins of the present reign are made by Mr. Wyon, and 
the beauty and high finish of the present five-pound pieces 
are a theme of universal admiration. As the workmanship 
of the coins during a whole reign depends entirely upon the 
skill of the artist, and as in centuries hence the state of the 
arts in our time will be inferred from the workmanship on 
our coins, how important is it to secure the first talents for 
that object ; and having secured them to cherish them with 
a fostering care, and place within their reach every possible 
means that in any way, however remote, may contribute to 
the super-excellence of the work. The original sketch of 
the artist should always be copied in metal, either silver or 
copper, and carefully preserved ; one copy being sent to the 
British Museum, another to Oxford, and a third kept at the 
Mint. By these means posterity would be enabled to have 
the identical likeness of each sovereign, that served as a 
model for the artist from which to make all his other works. 
A copy of such a sketch should always be placed under the 
foundation-stone of large buildings. To return to our sub- 
ject — a plaster-cast is then taken from the wax mould, and 
a cast is generally made from it in iron, which is placed in a 
lathe, first employed in the French Mint : a blunt point 
passes from the centre of the object spirally over its entire 
surface, and is forced into all the depressions. This point 
communicates a similar motion to a cutting instrument, 
which cuts out an analogous impression on a piece of steel. 
This is repeated many times, by which at last a die is formed. 
This is required to be highly finished by the artist who made 
the original model, so that the proper feeling and expression 
may be given to the die. This die is then hardened and 
used as a punch, by which another steel relievo is made by 



THE mint. 263 

a very powerful press. After this second punch is formed, 
it is hardened and used to form the dies employed for coin- 
ing. Pieces of metal of the exact size and weight of the 
coin are then prepared by a series of operations, and made 
very clean previous to coining. In the Mint, the pieces of 
metal are placed in a hopper, and one by one is let loose by 
mechanical contrivances and conveyed directly under the 
die which is connected with a piston communicating with a 
vacuum. The pressure of air on the piston causes the die to 
descend with great force upon the object, and the piece of 
money is immediately thrown out coined. Such is the 
rapidity of the operation, that notwithstanding the immense 
outlay in the first instance for the apparatus, and the expense 
of making dies, the cost of each coin is very far short of 
what would be incurred by electro-metallurgy, even if we 
were able to make perfect medals by that process. 

I have seen another method used for coining. A punch 
is taken, on which one side of the coin is engraved. Over 
this an iron collar is placed. A second die is then made 
with the opposite side of the coin, to fit into the collar. A 
piece of metal is then placed between both, and a smart blow, 
or a series of blows makes the impression. 

However, the success of mechanics over electricity has its 
limit, for as soon as the medals begin to be larger, one blow 
will not suffice to bring up an impression ; two or three are 
required, and between each blow the medal has to be placed 
in a furnace and annealed, as the compression of the first 
blow would incapacitate it for receiving a second with any 
advantage. The largest medal ever struck was the medal of 
Boulton, of which some impressions it is said had 300 blows. 
The beautiful medals now being engraved by Mr. Wyon 
and Mr. Leonard Wyon, as prizes for the Exhibition, will 
probably require nearly 200 blows to obtain their full per- 
fection. Here electricity begins to show its utility, and for 
all larger medals will for ever totally supersede every mode 
of casting. Fine medallions of the Duke of Wellington and 



264 TOMES'S CARVING APPARATUS. 

Sir Robert Peel have lately been modelled by Palmer, and 
multiplied by his brother. 

A machine, differing somewhat from that used at the Mint 
for copying dies, has been invented by Mr. Tomes, for cut- 
ting those parts of artificial teeth which rest upon the gums, 
to which they require to be adapted with great accuracy. 
Mr. Tomes's carving apparatus consists of three slides, two of 
which are placed in the vertical plane at right angles to 
each other, while the third occupies the horizontal plane, 
with its motion at right angles to the motions of the other 
two slides. The model to be copied, and the material in 
which the copy is required, are fixed side by side on a plate 
of metal operated on by the slides situated in the vertical 
plane, while a tracer and a drill are fixed on a plate of metal 
which moves in the horizontal slide. The various slides are 
set in motion by mechanical arrangements, and in such a 
manner that every part of the model is passed over by the 
tracer, which accurately governs the motion of the drill, so 
that a perfect copy of the model is produced during the 
operation. 

This machine, though invented by Mr. Tomes for the 
purposes of his own profession, is equally suitable for pro- 
ducing copies of medals. But, like all machines which 
produce the copy by means of a rapidly revolving drill, it 
leaves a little work to be finished by hand where acute angles 
are required. In artificial teeth all the surfaces are curvi- 
linear, hence the machine finishes the work with an accuracy 
of detail which the hand cannot equal ; but in copying a 
coin, all sharp angles, such as those about the letters in the 
inscription, require to be picked out with an engraver's tool. 

Hitherto we have been speaking of the comparative value 
of different modes of making original medals ; but let us 
compare electro-medals with other casts used by numisma- 
tists. Now there are only two substances much used for this 
purpose, and these are sulphur, and plaster of Paris. For- 



CASTS OF COIK8. 205 

merly the obverse and reverse were arranged side by side on 
one piece of sulphur, wound round with paper gilt at the 
edge ; latterly, however, it has been the fashion to make the 
cast exactly like the original, the obverse being on one side 
and the reverse on the other. Now the obverse and reverse 
of electro-medallions, after having been filed flat, can very 
readily be joined together with a little glue in such a way as 
to render it almost impossible to distinguish the point of 
junction : and it must be a matter of taste, whether the two 
sides should be kept separate or joined together. The great 
superiority of electro over other casts must be apparent to 
all, especially when we consider that the duplicate may be 
made exactly to resemble the original, not only in work- 
manship, but also in the nature of the metal of which it is 
composed. If the medals are gilt, or of gold, they will show 
to greatest advantage if arranged on a green ground; if 
silver, or plated, on a light blue ; if bright copper, on a black ; 
but if bronze, on a pale yellow ground. 

Casts of entire coins may be made in sulphur, britannia 
metal, or plaster of Paris, by making a plaster mould of 
either side of the coin, and so adjusting the two moulds, 
which should be twice or three times the width of the coins, 
that the obverse and reverse are separated to the same amount 
as that of the thickness of the coin. A little channel is then 
cut, into which the sulphur, fusible or britannia metal may 
be poured out ; in that way a cast of the coin is accurately 
made. Now if any man should look into this book for a bad 
purpose, he will probably peep into this chapter; and let 
me now warn him of the consequences which must inevitably 
ensue from carrying out improper proceedings. Sooner or 
later he will be inevitably banished the country. There is 
an organized staff always watching for delinquents, and no 
expense is spared in their prosecution. I can assure the 
man who can successfully turn a knowledge of casting or 
plating to a bad account, that he possesses abilities and know- 

13* 



LIST OF COINS. 



ledge which would enable him successfully to obtain an 
honourable livelihood. If the advancement of science has 
placed within his means processes which may be turned to 
bad account, a corresponding advancement of science will 
render his detection not only more necessary but more easy. 

As to the coins the electro-medallist should select for his 
operations ; he should begin with the Jewish shekel from its 
historical associations ; he should then copy the exquisite 
specimens of Macedonian coins, in which series those of the 
renowned Alexander and Philip of Macedon are contained. 
He should then select the extraordinary productions of the 
Syrian empire, the race of the Seleucidse being much es- 
teemed for their beauty. He may continue with Alexander's 
other generals, the Ptolemys, &c. In his road the electro- 
metallurgist must not neglect the Syracusan coins — the 
finest the world has ever produced — nor pass unnoticed the 
Carthaginian series, nor forget the relics of the former 
grandeur of the Greek Islands. The Roman empire next 
demands consideration, and the Caesars must be copied. The 
medallist may copy a few more Roman medallions and coins, 
after our Saviour's time, and then pass to the early British, 
of which the Saxon should be the beginning of the series ; 
after which, he should continue through the various reigns 
to modern times. Having completed such a series, the 
electro-medallist should arrange them in chronological and 
geographical order, and he will find that he has made an 
epitome of history, in which the progress of the arts may be 
traced through upwards of two thousand years. The high 
state of the arts in Greece, with their subsequent fall to the 
degradation into which the world had sunk under monkish 
dominion is striking, and their rise to the reign of the un- 
fortunate Charles, about which period the Symons executed 
their splendid works, is remarkable. The slight vacillation 
of the numismatic art from that period to the present time 
may also be traced. 



LIST OF COINS. MEDALS, ETC. 267 

Those who prefer medals to coins may select the finely 
cast and chaste medals of France and Italy, the medals of 
William and Mary, the Napoleon medals, we should not 
forget the medal struck by the Pope to commemorate the " to 
him" glorious massacre of St. Bartholomew, those of the 
kings of France, and Wyon's latest productions, of which to 
my taste the medal executed for Prince Albert is the most 
exquisite. 

The finest collection of coins and medals at the present 
time in the whole world, is at the British Museum, and 
when that establishment has an electro-cast of every other 
coin or medal that is known, either in copper-gilt, silver, or 
bronze, so as to resemble the original, then indeed may 
Englishmen be proud of their national collection. It w T ould 
not be difficult to arrange casts of every known medal in a 
room open to the public. 

Where we desire electro-medallions to have a very 
perfect rim, it may be accomplished by winding round the 
mould a thin piece of sheet lead, copper, or such like metal, 
and allowing it to project about one-eighth of an inch be- 
yond the edge, when it will be found, that on the completion 
of the process the electro-medallion will have a rim of that 
depth. 

(227.) There are many eminent persons distinguished for 
their learning, their abilities, their public station, or their 
private virtues, a medallion of whom would be greatly 
esteemed by their friends. Now the expense of engraving a 
steel-die in a first-rate manner, is such, that it altogether 
precludes the idea in ordinary cases ; but as soft substances 
can be copied by the galvanic process, the expense of obtain- 
ing a medallion in wax, when divided among thirty or forty 
persons, would surely not be a material object, and they 
would be thus enabled to possess a likeness of the person so 
much endeared to them. What a contrast would there be 
between the distribution of the portrait of a deceased and 



268 PERFECT ELECTRO-MEDALLIONS. 

esteemed friend, and the unmeaning custom of giving a black 
and gold ring, simply bearing an inscription ! How much 
better would the remembrance be perpetuated ! for the ring 
is valued more frequently for its size and intrinsic worth, 
than for the remembrance it is intended to convey ; and 
after having been worn for a year, is too frequently cast 
without remorse into the melting-pot. A copper or silver 
medal, on the contrary, no matter how beautiful its execu- 
tion, would intrinsically be worth only a few pence, and fre- 
quently would be far more prized and taken care of by the 
possessor. 

(228.) It is a great desideratum to be enabled to take a 
perfect coin or medal by electro-metallurgy, that is, one 
having both obverse and reverse ; as yet this has not been 
obtained, and from my experience it appears to me to be 
very difficult. The manner in which I have attempted to 
attain this object has been, to procure casts of both sides of a 
medal, and to place these in contact at the part of the plaster 
external to the impression, in such a manner that a distance 
intervened equal to the width of the coin ; the inner surfaces 
of the plaster-casts were then black-leaded, and connected 
with the zinc of the battery, whilst the piece of copper to be 
dissolved was placed above a little hole left in the rim of the 
plaster-mould. In this position the moulds were connected 
with the silver of the battery ; but the process with me did 
not succeed. I conceive, however, that it is possible, by 
this method, to make a thick medal with both obverse and 
reverse. 






2G9 



CHAP. II. 

ON COPYING SEALS, PLASTER CASTS, ETC. 

Value of a seal, 229. Process for copying a seal, 230. Copper moulds 
from plaster medallions, 231. Quality of the reduced copper, 232. 

(229.) In former times, when the art of writing was an 
extremely rare accomplishment, a seal was an instrument of 
great importance : it fulfilled the same purpose at the end of 
a conveyance or deed that is now accomplished by the written 
names of the parties; which even now, in reference to the 
ancient custom, are termed signatures. No business was 
performed without the seal, no corporation existed without 
this appendage. The extraordinary seal of Southwick, which 
required three separate dies to form one impression, is a 
good instance of the important functions of the seal ; for the 
three parts being in the respective hands of three trustees, 
it required the concurrence of all, before a perfect impression 
could be made ; and consequently, before any land or other 
property under the trust could be disposed of. Now the 
value of the seal is nearly lost, and in the great establishment 
where I lately resided, thousands of pounds hourly change 
hands without any such ceremony ; a faint representation 
only of the seal being made by a black wafer, a bare relic of 
former customs. 

(230.) Now that seals are nearly valueless, there can be 
no harm in describing the process for copying them. This is 
very simple ; we first give them the thinnest film of black- 
lead, with a hard brush. If necessary, this may be aided by 
cautiously applying the most minute drop of spirits of wine, 
but it should be avoided if possible ; for the wax being soluble 



210 PROCESS OF MOUNTING SEALS. 

in alcohol, the seal is liable to more or less injury. A fine 
metallic wire is now to be heated over a candle, and the hot 
end placed in contact with the rim of the seal so that it may 
adhere. Care must be taken to apply a little plumbago 
round the point of insertion, that it may be continuous with 
the wire. It is then ready to be placed in the solution. This 
part of the operation is similar -in all respects to that required 
for the moulds of coins. (220, 221, 222.) 

After the seal is removed from the wax, it is usual to mount 
it by soldering it on to a piece of metal, and then to fix it on a 
turned handle for the convenience of using. 

Considerable care is required to effect this purpose, the 
seal must be first cleaned at the back with charcoal and 
water, and then dried. A little powdered rosin is sprinkled 
on the back, and the medal is then held in the flame of a 
spirit-lamp till the rosin begins to smoke, when a stick of 
soft solder is rubbed over it, and as soon as the solder adheres 
all over and fills up the hollows it is allowed to ceol. The 
seal is then placed face downward on a cork, and with a file 
carefully reduced in thickness till the edge of the copper is 
apparent all round, but care must be taken to keep the two 
surfaces quite parallel. If the seal is very thick, the filling 
with solder may be dispensed with, as the copper in that 
case may safely itself be filed flat. A piece of metal, either 
copper or the alloy known as red gun metal (an alloy of 
copper and tin), is then prepared with a flat surface at one 
end sufficient to cover the seal, and with a socket at the 
other, to which a handle of either agate, ivory, ebony, or 
other hard wood, may be fixed. The flat part of the handle 
must be coated with a thin layer of solder, and that, together 
with the prepared surface of the seal, sprinkled with a little 
rosin, when the two surfaces are placed in accurate contact, 
and then held in the flame of a spirit-lamp until the solder 
melts and unites the two, the edge is then to be carefully 
filed and polished, and the face of the seal cleaned by char- 






PROCESS FOR COPYING PLASTERS. 271 

coal and water. In those cases where the device is very deep 
it will not admit of being reduced perfectly flat, and in that 
case the rim is filed to the same extent all round, and an 
indentation must be cut in the handle corresponding to the 
elevation at the back of the seal. 

The largest seal, as the great seal of England, or the large 
seals of the bishops, may, in this way, be copied with ease ; 
and the smallest are attended with no more difficulty. The 
operator must remember, that although he is at perfect 
liberty to copy the Chancellor's seal of the last reign, yet he 
would be liable to the utmost penalty of the law if he were 
to carry on his scientific proceedings upon the great seal of 
Her present Majesty. A letter received in the morning may 
be answered the next day, or even the same night, by a letter 
sealed with an electrotype impression of your friend's seal. 
If a relievo be required from a sealing-wax relievo, it may 
be obtained by a double electrotype operation, or by first 
making a plaster intaglio, and proceeding with that as for 
plaster generally. Seals may be made either in silver or 
copper, the processes for which are similar, in all respects, to 
that described for making electro-medallions. 

(231.) Copper or silver moulds may be obtained of the 
utmost perfection, from plaster medallions. If we desire to 
take a copper mould or intaglio from a plaster relievo, we 
simply prepare the plaster by tallow, wax, or any other simi- 
lar substance. We then carefully apply the black-lead, and 
twist round the rim fine wire to connect it with the battery, 
after which it is ready to be placed in the metallic solution. 
The copper or silver copy is by these means as perfect as the 
plaster. When a relievo of a plaster medallion is desired, we 
may either electrotype the copper mould obtained as before, 
or we may make a mould of white wax, having first filled the 
plaster with water. The wax mould is to be blackleaded, 
and must have a wire attached to it, before it is put into the 
solution. The compound of bees'-wax and rosin may be 



272 HARD COPPER METALS. 

used for the same purposes, its application being similar to 
white wax. The medal produced by any of these means is 
quite perfect, and the process is an excellent one ; for it is 
neither attended with difficulty, nor does it require much 
labour, and is performed without the slightest detriment to 
the original plaster medallion. The whole difficulty attend- 
ing the multiplication of works in plaster, is not the manu- 
facture of the copper duplicate, but the trouble of obtaining 
the plaster itself perfect. It is singular that every artist 
who uses this substance, considers that he is possessed of 
some secret ; but in re'ality, the working in plaster is nothing 
but an art acquired by practice, and requires judgment in 
different cases. A full description of all the minutiae requiring 
attention has been already detailed. 

From a plaster cast we can obtain a stereotype mould, 
and from this a medallion in copper, silver, <fcc. ; but few 
now would be inclined to follow this method when others are 
so well adapted. The apparatus and modus operandi are 
similar, in all respects, to that employed for the multiplication 
of coins and medals. (220 — 222.) 

(232.) The reduced metal, be it silver or copper, for the 
foregoing objects, can be made of any texture that may suit it 
best. It may be either produced of the greatest flexibility, 
or of the most extreme hardness, by following the laws which 
we have laid down. A very hard medal, cameo, or seal, is 
best obtained by using a very strong solution, a single battery, 
and a large positive copper pole. It might be very useful 
for Bate's Anaglyptograph, an ingenious instrument, by which' 
a correct engraving of any raised object can be executed. A 
point is passed over the medal at an angle of 45°, this com- 
municating a motion to a diamond point. As the point 
passing over the medal is raised or depressed, the diamond 
point takes a corresponding curve, so that the lines ruled on 
the plate form certain curves, the effect of which is to give a 
correct drawing of the medal. When a thin layer of black- 



HARD COPPER MEDALS. 273 

lead is used, the deposited copper will not in the slightest 
degree be discoloured by it, as the plumbago will always be 
taken into it, leaving none on the prepared plaster. If a very 
thick layer of black lead is employed the copper will be dis- 
coloured. 

The hard copper is of great use to the metallurgist, as he is 
in the habit of using it for his machine, by which he mechan- 
ically forms the dies. 



2U 



CHAP. III. 

ON THE MULTIPLICATION OF BRASSES. 

Process for obtaining Duplicate Brasses, 233. 

(233.) There is scarcely a church in the country which 
has not some curious old monument where characteristic 
likenesses of a whole family are engraved on a brass plate. 
To the Town Council of Yarmouth these relics were of so 
little interest that they condemned the whole collection from 
one church to be applied to the manufacture of standard 
weights for the use of the town. By some clergymen and 
churchwardens they have been regarded as legitimate mines 
of wealth, as they have been frequently sold as old metal, 
either to enrich themselves or to benefit the parish. By 
antiquaries, however, these monuments are highly prized, 
and many would be delighted to possess a fac-simile of many 
of these objects. This may be accomplished by comparatively 
simple means. It is only necessary to take a cast of the 
brass in gutta percha or plaster of Paris, having previously 
oiled the brass ; if plaster is used, it is to be well dried, and 
then soaked in tallow. A wire must now be passed round 
it, and black-lead applied with a soft brush, when it is ready 
to be connected with the battery. Only moderately-sized 
brasses can be copied in this manner, for some are so large, 
as that of the Archbishop of York in Chigwell church, in 
Essex, or those in Westminster Abbey, that they would 
require such large vessels as virtually to render the manufac- 
ture of a duplicate almost impossible. 

The battery process is best suited for these purposes. A 



ON THE MULTIPLICATION OP BRASSES. 27 5 

large piece of refuse copper must be employed for the positive 
pole, and it should be placed as near the plaster as possible. 
As a large surface of plaster is generally required to be 
copied, a large battery will be required, otherwise the 
strength of the metallic solution must be regulated to the 
power, and rendered much more dilute and acid. 

A great taste has lately arisen for studying monumental 
brasses. The lover of these objects prowls over the country 
with a roll of lining paper in his hand, and a packet of heel- 
ball* in his pocket ; and wherever he finds one of these 
much-prized brasses, he places the paper over it, and rubs the 
surface of the paper with heel-ball, which blackens it, except 
at those parts immediately over the incised lines. This mode 
decidedly gives the clearest impression, but some antiquarians 
prefer a mixture of linseed oil and black-lead, about the consis- 
tence of mustard, which they apply to tissue paper with a 
leathern rubber. For further particulars relating to these 
curious matters, the student must refer to works peculiarly de- 
voted to these remains, but especially to those exquisitely beau- 
tiful and accurate illustrations of monumental brasses by the 
Wallers ; a work already in the library of every person having 
the slightest pretensions to a knowledge of the antiquities of 
Great Britain. 



* A composition used by shoemakers to rub over the heels and sides 
of the boots and shoes. 



276 



CHAP. IV. 

ON MAKING DIES FROM EMBOSSED SURFACES. 

On metallic reverses from raised surfaces by galvanic agency, 234. 
Peculiarities of dies made from paper, 235. 

(234.) All embossed surfaces may be copied with facility, 
whether they consist of paper or any other substance. They 
must be first rendered non-absorbent by oil, varnish, or wax, 
according to the thickness of the mixture ; linseed oil, perhaps, 
is to be preferred for paper. It must be allowed to dry before 
the black-lead is applied to make it ready for the solution. 

(235.) Dies made from paper generally exhibit a slightly 
dented appearance in the smooth parts, from the little project- 
ing points of the paper having been copied. This, it is said, 
disappears after many impressions have been printed. 

A hard copper die formed from sealing-wax or other impres- 
sion would in all probability be applicable to the formation of 
stamped wafers now so much in use. Since my last edition the 
use of these dies has been much extended by Mr. Barclay ; and 
at the present time, a book of coins is published, in which a 
hundred different coins are illustrated by fac-similes in tin-foil 
or paper, the impressions of which have been struck from these 
copper dies. Colonel Leake has also a book illustrating his 
rare and curious Greek coins in a similar way. 



277 



CHAP. V. 

ON THE MANUFACTURE OF MOULDS FROM FRUITS, 
VEGETABLES, ETC. 

On making moulds from vegetables substances, 236. Chantrey's 

method, 237. 

(236.) In a former book, means were adverted to for 
coating various kinds of fruit, vegetables, and leaves with 
metallic copper, having first black-leaded them. (207.) By 
simply carrying on the process until a thick deposit be 
obtained, instead of merely coating the object, a mould will 
be obtained for any purpose required. A cast thus taken 
of a leaf, for instance, that of a Morel cherry, baffles all 
description. The copy is absolutely perfect ; every fibre 
and nerve, in fact the minutest part, is cast in copper with 
the utmost fidelity ; and in the same way the surface of 
fruit may be correctly copied, so that every excrescence 
or depression, however minute, will be as apparent as in the 
original. 

(237.) Sir Francis Chantrey had a very ingenious, though 
a troublesome and complicated, method of obtaining a cast 
of leaves or sprigs of trees ; he takes the finest river sift, 
ground up, and encloses the leaves and sprigs in it; the 
whole is then dried and thoroughly baked, by which process 
the wood is carbonised ; a strong blast of air is then sent 
through the apertures, which removes the carbon and 
leaves a cast of the object, and that serves as a mould, into 
which he pours his melted copper. The same end might 
be attained in some cases far more readily by the galvanic 
current. 



278 METALLIC MOULDS. 

Every vegetable and animal substance whatever, which 
will remain undecomposed in the solution of copper for a 
few hours, can have a metallic mould made from it. For 
nearly all these cases the battery apparatus, similar to that 
used for medals, is the best. 



2V9 



CHAP. VI. 

ON THE APPLICATION OF ELECTRO-METALLURGY TO SCULPTURE, 
BAS-RELIEFS, AND OTHER PURPOSES. 

The mode the sculptor adopts to obtain a metallic cast, 238. On making 
a metallic cast by Electro-Metallurgy, 239. The texture of the copper, 
240. General remarks, 241. On the application of Electro-Metallurgy 
for goldsmiths, 242 ; for surgeons, <fec, 243. 

(238.) Unfortunately the British public have nearly ceased 
to patronise British sculpture, otherwise electro-metallurgy 
would be a valuable assistant to that art. The sculptor first 
makes his model in clay, from which he takes a cast in plaster, 
and this again serves as a mould, into which he pours his 
fused metal. This latter proceeding is attended with much 
trouble, and not unrrequently with great danger from a risk of 
explosion. The metallic cast when made is by no means per- 
fect, as it requires much labour to finish it. 

The electro-metallurgist could obtain a far more perfect cast 
at once, by simply preparing his plaster, black-leading it, and 
placing it in the solution of sulphate of copper. A wire in con- 
tact with the black lead must communicate with the zinc of 
the battery, whilst the sheet of copper to be dissolved should 
communicate with the silver. 

(239.) For very large designs, an inconveniently large 
vessel would be required ; to obviate this difficulty, the 
mould, provided it be hollow, might have the separate pieces 
of which it is made so joined together by wax or grease that 
itself should form the vessel to contain the liquid. Very 
large batteries ought to be employed by the sculptor, and 



280 COST OF THE PROCESS. 

rather a dilute solution ; because, in all probability, the size 
of the battery will not be proportionate to the immense 
surface exposed in even a moderately-sized design. The 
piece of copper forming the positive plate should be as large 
and as close to the plaster mould as it can be placed, in 
order that as little impediment as possible may be afforded 
to the passage of the current. 

(240.) The copper may be of any thickness ; and its 
strength and thickness may be regulated, as required in 
different parts, by increasing or diminishing the distance 
between the various parts of the plaster and the positive 
plate of copper. The relative cost of this method of making 
a bronze figure, to that of the plan now in use, is, perhaps, 
difficult to estimate accurately. By the old plan a bronze 
figure costs the value of the copper and the coals required 
for its fusion, besides the labour requisite to render the 
metal cast perfect afterwards. By the galvanic method it 
would cost the value of the copper, + the value of an equal 
weight of amalgamated zinc, + the cost of the labour re- 
quired to work the batteries — the value of the sulphate of 
zinc formed. From the * above statements, a rough idea 
only can be formed of the relative cost of these two methods 
in practice, and it can only be determined with certainty by 
very large operations. 

I do not know that I can give any more accurate notion 
of the power of electro-metallurgy, than to notice that it 
can copy a Barton's button with the most perfect accuracy. I 
have an electro cast of a Barton's button in copper, which 
was given to me by Mr. Poulton, one of our preparers of micro- 
scopic objects, of whom, I believe, they can be purchased. The 
specimen is now upon my paper, and the dazzling brilliancy 
of the colours is so great, that it painfully distresses the 
eye to observe it at the reflecting angle. Perhaps it is 
hardly necessary to remind my readers, that the lovely 
colours which it presents are due to lines ruled exceedingly 



COPYING COLOURS OF MOTHER-OF-PEARL. 281 

close together. These electro casts might doubtless be used 
for ornamental purposes. 

In Mr. Timbs' valuable Year Book of Facts for 1847, a 
record is made of certain experiments performed by Pro- 
fessor Silliman in America, in which he most successfully 
copied the iridescent colours of mother-of-pearl, and the 
process of which appears to be of sufficient importance to 
transcribe : — 

" A few months ago, while engaged upon some experi- 
ments in electrotyping, I was led to think that by this process 
the hues of the pearl might be readily transferred to those 
metals which, from their hardness, are incapable of receiving 
impressions in mass ; but yet on account of their freedom 
from oxidation retain for a long time a surface compara- 
tively pure. I therefore took a Smee's battery which I 
had just constructed, and after several experiments suc- 
ceeded in obtaining small sheets of silver radiant with the 
hues of the shell. When seen by a single light as that of 
a lamp, the play of colours is surpassingly beautiful, scarcely 
inferior to that of the pearl, .and where equal care was 
employed, the plate of silver which was formed eight 
months ago rivals in brilliancy that which came fresh from 
the battery a few hours since. 

" The process by which this result is obtained is as follows : 
— The first thing required is to prepare the shell. This is 
effected by grinding and polishing it upon the back in such 
a manner as to cut through the numerous concentric strata 
that compose its substance. When this is done by the aid 
of a microscope the surface will be seen covered with 
delicate grooves, some thousand in an inch, formed by the 
sections of the concentric laminae, and this configuration 
gives rise to the glowing tints of the shell. The next step 
is to obtain an exact impression of this surface upon some 
good conductor of electricity. This we are enabled to do 
by means of fusible metals, if proper precautions are em- 

14 



282 APPLICATIONS OF ELECTRO-METALLURGY. 

ployed in taking the impression. I pursue exactly the 
same method as in taking the copy of a medal. After 
fusing the metal, I pour it upon oiled paper, and when the 
air bubbles cease to rise through the metal, the oxide is 
skimmed from its surface with a card, and as soon as it 
presents the appearance of a perfect mirror the shell is 
forced down upon it by a sudden pressure. When the 
metal has cooled I remove it from the shell, and having 
ascertained the accuracy of the impression, immediately 
plunge it before any change of the surface can occur, 
thereby completing the circuit between the poles of the 
battery. In a few moments the surface of the metal is 
frosted with silver, and the configuration of the shell exactly 
copied. A sheet of silver of sufficient thickness to be easily 
removed with a penknife will be deposited in the course of 
five or six hours under favourable circumstances." 

Electro-metallurgy is now found of the utmost value to 
the model maker. I have lately seen some parts of a most 
beautiful model which is being manufactured by Mr. James, 
the eminent model engineer, for the Great Exhibition. It 
is a perfect representation of the Menai Bridge, showing 
its construction, and made to scale. The tubes were de- 
posited in parts which were afterwards soldered together 
and electro-silver-plated. Another model of the great sus- 
pension bridge over the Dniester had the abutments electro- 
silvered so correctly to imitate stone that the eye may 
be easily deceived on inspecting it. 

Mr. Chaterton, who executes exquisite carvings of ivory by 
means of a peculiar machine, exhibited last winter at the 
various scientific soirees a skull bust prepared by electro- 
metallurgy. His modus operandi was to form a cast of the 
head, and coat it with copper, and then to remove the interior 
cast. In the copper mould thus obtained, he deposited a 
copper reverse ; but the whole operation is subject necessarily 
to considerable difficulties requiring continual watching. The 



GENERAL REMARKS. 283 

bust he exhibited was very perfect, but the exact means he 
used have not been published. As far as regards the electro- 
metallurgical process, the solution, positive pole, &c, must 
be regulated by the principles so fully detailed in former 
parts of the work. 

(241.) Before bringing this book to a conclusion, I may 
mention that the application of electro-metallurgy, or the art 
of working in metals by the galvanic fluid, is not confined to 
the foregoing subjects ; for every kind of object which can 
possibly be made in copper by any other method, can also be 
made by electricity. With regard to the use of other metals 
for the like purpose, they can in some instances be employed ; 
but still, the application of the galvanic fluid to the working 
of these must be limited, because the intrinsic value of many 
is so great as to preclude their general use ; whilst the value 
of others is so trifling as to render their application of little 
value. 

As a general rule, all articles of tin, lead, iron, and zinc 
are infinitely better and far more cheaply made by the 
present mechanical processes than they could be by electro- 
metallurgy. I do not pretend to say that there may not 
be some particular cases in which the pure metal obtained 
by the latter process might be preferred to the impure 
metal. Pure iron might be valuable, pure zinc might 
be useful, but, for all manufacturing purposes, there is but 
little doubt that the cheapness, ease, and, above all, the 
capability which mechanics possess of an unlimited pro- 
duction of articles by the steam-engine gives a vast pre- 
ponderance in its favour, especially when we consider the 
mind continually required to superintend and direct voltaic 
processes. 

P'or articles of copper, the benefits of electro-metallurgy 
do not manifest themselves whenever the cost of the work- 
manship is not equal to the cost of the voltaic reduction, and 
whenever the object can be made by pure mechanical means. 



284 GENERAL REMARKS. 

as the latter in these cases are mostly to be preferred to 
chemical means. As soon, however, as the cost of the 
materials and labour exceed those required by the chemical, 
then does electro-metallurgy begin to be advantageous, and 
the multiplication of all elaborate and highly finished articles 
should be effected by the latter process. In a former part of 
this work data for ascertaining the expense of the various 
processes, comprising electro-metallurgy, have been quite 
sufficiently considered. Although, however, throughout 
this work the relative cost of processes has been continually 
discussed, let me once again strongly urge the manufacturer 
to pause before he introduces electro-metallurgy and sub- 
stitutes it for former modes of manufacture. Excellence and 
economy are the only circumstances that he has to regard in 
a business point of view ; and he has no right to consider 
the beauty of any particular process, or to be allured to apply 
electro-metallurgy for purposes not suitable to it, by the 
demi-magical phenomenon of an old worn-out nail and a dis- 
solved penny-piece being capable, after a few hours' patience, 
to form a duplicate of a work of art which required years for 
its first execution. 

Attempts have indeed been made to make copper tubes by 
electro-metallurgy, and also saucepans and similar vessels, 
but there is no doubt that those who practised this mode must 
have been ignorant of the relative expense of the processes. 
However, in this case, as in others, it is possible that tubes 
of peculiar curves might sometimes be made profitably by 
electro-metallurgy, and that the absence of soldering might 
be turned occasionally to advantage. 

Amongst the extraordinary applications of electro-metallurgy 
which have come under my notice, I may state tha£ it has been 
applied to coat the tops of wine bottles to endeavour to close 
them effectually from the atmosphere. 

Electro-metallurgy offers means for the multiplication of 
polished surfaces, but its benefit is confined to particular 



GENERAL REMARKS. 285 

cases, as highly burnished surfaces cannot be so perfectly 
multiplied, because if those surfaces are absolutely clean 
adhesion would take place, and if the air adheres to the 
originals a slight spotted appearance termed "a curd " 
is noticed, which would seem to be an irregularity in the 
thickness of the film of air. Although burnished surfaces 
cannot be absolutely and perfectly multiplied, yet for many 
practical purposes the process may be effected. The 
formation of duplicates of specula must be regulated by the 
preceding observations, for it would be requisite always 
to finish the duplicate by burnishing. All such delicate 
processes should never be attempted till experience has 
taught the operator how to overcome the difficulties likely to 
occur. 

With regard to the manufacture of silver articles by 
electro-metallurgy, the preceding observations equally apply. 
The manufacture of silver spoons and forks by the present 
process is effected so cheaply as to leave no shadow of doubt 
that it is infinitely to be preferred to electro-metallurgy. 
Very elaborate articles of which duplicates are required, 
might perhaps be advantageously made by electricity, and it 
is almost needless again to mention that the silver might 
be strengthened with layers of copper, should ever such pro- 
cess be required. One objection to electro-metallurgy for 
these purposes is the necessity for the employment of pure 
silver. 

(242.) To workers of gold electro-metallurgy promises to 
be occasionally of value ; for, after having once procured a 
mould, he can obtain the most elaborate devices ; but still, 
in buying manufactured articles of gold, the intrinsic value of 
this metal is so great that the workmanship forms frequently 
but a small part, — or otherwise electro-metallurgy might be 
of importance to the goldsmith. 

The dentist requires for artificial teeth an exact cast of the 
mouth in gold, platinum, or palladium. Now the cost of the 



286 APPLICATIONS OF ELECTRO-METALLURGY. 

manufacture of this is so expensive, that many are prevented 
from availing themselves of these valuable appendages. It is 
absolutely necessary that the gold should fit very accurately, 
or else the possessor is not able to use them. Electro-metal- 
lurgy might, perhaps, be brought to aid the mechanic in this 
matter, but the operator must recollect that notwithstanding 
the scientific principles detailed in this work, considerable 
skill in the manipulation would be required, especially as i fc 
is necessary that the metal should be of the utmost tenacity 
and firmness. 

(213.) Even to the surgeon, electro-metallurgy appears 
likely in some cases to be useful ; for when he is desirous of 
exerting constant pressure on any part, or of confining any 
part in a particular position, he can make a copper instrument 
exactly to suit any individual case by first taking a cast in 
gutta percha, plaster of Paris, or, in some cases, by a piece 
of gummed sheeting. At present no case has occurred in 
my own practice where such an application of electro- 
metallurgy has been required ; but I have seen cases of 
club-foot, where, doubtless, a metallic mould might have been 
applied with great benefit to the patient. With regard to 
metallic splints, perhaps in some cases they might be used 
with great advantage, but as a general rule those made of 
the moulding tablets or of gutta percha (such as I have de- 
scribed in the Medical Gazette) are more applicable. By a 
proper use of splints made of these moulding tablets many 
cases of broken limbs have occurred where the patients have 
been enabled to leave their beds and enjoy the comforts of 
the external air within three or four days of the accident. 
For these purposes splints made of gutta percha or of my 
moulding tablets would, from their lightness, be much pre- 
ferable to metallic splints, for though they may be made to 
take a perfect cast of the face, they yet set so firm and hard 
as to bear a very severe blow without accident. 

To the geologist electro-metallurgy is not without its in- 



VALUE OF ELECTRO-METALLURGY TO THE GEOLOGIST. 287 

terest, for, independently of the rationale which it affords of 
the veins of metals embosomed in the earth, it gives the 
means of obtaining in copper casts of any fossil which will 
remain unacted upon in the metallic solution. If the solution 
is acid, of course it will be unsuitable for any strata contain- 
ing carbonate of lime ; but then, by first taking an impression 
in plaster, a metallic reverse can be taken from it which will 
be a perfect fac-simile in metal of the original. These me- 
tallic casts are preferable to any other kind of duplicate, 
because they occupy less bulk, are lighter, less destructible 
and fragile than any other material. 

Electro-metallurgy is now brought to such perfection, 
that a copper cast of tenacious metal can be made of any 
size or form ; and it may be even painted to resemble the 
object it is intended to imitate. All other materials, as far 
as possible, should be discarded from our museums, as for 
nearly all purposes the copper is entitled to a decided 
preference. 

Mr. Poulton has lately sent me an electro cast of the eye 
of a dragon fly, which under the microscope exhibits perfectly 
all the facets common to a compound eye. This must be 
regarded as a very remarkable application to this ingenious 
manipulation. 

The architect should always bear in mind the powers with 
which electro-metallurgy furnishes him. By it he will be 
enabled to introduce at but moderate expense, relievos, or- 
naments, statues, friezes, &c. &c, into the composition of 
his building. In the construction of churches, electro-me- 
tallurgy, if used rightly, is Capable of adding great effect. 
If electro-metallurgy, only in a slight degree, should cause 
us to return to the splendour with which Solomon considered 
that buildings dedicated to worship should be constructed, 
then, indeed, will all who have assisted in developing its 
laws and facilitating its practical application be proud ; for 
there is no national disgrace more to be deplored, than that 



288 VALUE OF ELECTRO-METALLURGY TO THE ARCHITECT. 

buildings erected for dancing, feasting, or debauchery, should 
be fitted with all the embellishments which modern science 
has so abundantly supplied, whilst, too frequently, buildings 
not sufficiently excellent to be used as kennels for the hounds 
of the nobility are thought amply splendid for consecration 
to the worship of the Almighty ! 



289 



BOOK THE FIFTH. 

ON THE ELECTROTYPE. 
CHAPTER I. 

ON THE MULTIPLICATION OF TYPE. 

The mode of printing books, 244. On stereotyping, 245. On Electro- 
typing the type, 246. 

(244.) The ordinary type, such as this work is printed with, 
has each letter separately cast of a particular alloy ; these 
letters when combined together form words ; again, a number 
of words form a paragraph — a series of paragraphs a chapter 
— a number of chapters a book — and lastly, several books 
form this volume. Most works are printed in parts; thus, 
whilst I am writing this chapter, the second book is com- 
pletely printed, and the types distributed, whilst the proof of 
the third is lying on my desk to receive such alterations as 
may occur to me. JSTow the electrotype would be of no 
value to the printer in this case, for the same type which is 
used for the first part of this work, will be again used for 
the last, and even after the whole is printed, will be very little 
impaired. 

(245.) With books which have a very large circulation, as 
the Bible or Prayer-book, and where no changes are required 
in the matter for a series of years, it is usual, after the work 
is completely set up in type, to make a stereotype copy of it. A 
plaster mould of the .type is first obtained, which is thoroughly 
baked in an oven, and from this a metallic cast in stereotype 
metal is made, which is a copy of the original. The duplicate 
thus obtained is slightly impaired by the injury which the 
plaster east receives in the furnace, otherwise it has advan- 

14* 



290 ON THE MULTIPLICATION OF TYPE. 

tages over the type ; for every stereotype page is in one piece, 
whilst the type is made up of as many different pieces as 
there are letters, besides numerous pieces termed leads, &c. 
The process of stereotyping is cheaply effected, but the electro- 
type may be made more perfect. An attempt is now being 
made to introduce a new material, apparently a composition of 
shell-lac and other matters, for the purpose of forming the cast. 
The mould is made of plaster of Paris, and the material is fixed 
unto a cast block to keep it perfectly steady. The material is 
said to be brittle, but nevertheless to print satisfactorily. I 
have seen a very beautiful cast made in this manner, but it has 
not yet sufficiently come into use to tell how far it will answer 
its intended purposes. The process of casting has yet ma- 
terially to be improved, as a more rapid mode of conducting 
the process is required. 

(246.) To procure an electrotype copy from a page of type, 
we have to take an intaglio impression from the type, which is 
most conveniently effected by making a cast m gutta percha : 
it may also be effected by taking a cast in sealing-wax, or in 
plaster of Paris, which must afterwards be rendered non-absorb- 
ent, or we may take it in white wax ; the intaglio impression 
must be black-leaded and placed in the solution to receive the 
deposit of copper. Great care must be taken to disperse air- 
bubbles. A moderately thin layer of copper would suffice, if it 
were backed with solder, type metal, or some such analogous 
alloy. This process is only likely to be useful for the Bible, 
Shakspeare, Pilgrim's Progress, or works that have a large cir- 
culation ; and, probably, might be found to wear longer and 
print better than the usual stereotype metal : but at present we 
have no experience on that matter ; though there is but little 
doubt that for these purposes electro-metallurgy will eventually 
be preferred. Up to the present time this has not been 
brought extensively into use from its difficulty and expense, but 
now, doubtless, it will be sometimes employed, as gutta percha 
materially diminishes the cost. A Frenchman has attempted 



ANASTATIC PROCESS. 



291 



the mechanical manufacture of type in copper ; the specimens 
I saw appeared to be good, and register truly, but up to this 
time it has not become an article of commerce. 

A very useful process has been added to printing since my 
last edition Avas written : it is called the anastatic process. If 
a page of print be washed over with phosphatic acid, an acid 
which is formed by the spontaneous combustion of phosphorus 
in contact with air and water, it appears to have the effect of 
starting the ink, and when the paper is then subjected to great 
pressure against a zinc plate, a copy of the impression is made 
upon the zinc, which, on being rolled as by the ordinary mode 
of lithographic printing, may be used in a similar way. The 
anastatic printing is now continually being used for repro- 
ducing any sheet which happens to be defective when an im- 
pression of a work is nearly sold. 

[Specimen of Electrotype^ 



MORNING PRAYER. 



such a Book : And after every I 
Lesson, Here endeth the First j 
or the Second Lesson. 

Te De-am Laudamus. 

WE praise thee, O God : we 
acknowledge thee to be 
the Lord. 

All the earth doth worship 
thee : the Father everlasting. 

To thee all Angels cry aloud : 
the Heavens, and all the Powers 
therein. 

To thee Cherubim, and Sera- 
phim : continually do cry, 

Holy, Holy, Holy ; Lord God 
of Sabbaoth ; 

Heaven and earth are full of 
the Majesty : of thy Glory. 

The glorious company of the 
Apostles : praise thee. 

The goodly fellowship of the 
Prophets: praise thee. 

The noble army of Martyrs: 
praise thee. 

The holy Church throughout 



We therefore pray thee, help 
thy servants: whom thou hast 
redeemed with thy precious 
blood. 

Make them to be numbered 
with thy Saints: in glory ever- 
lasting. 

O Lord, save thy people : and 
bless thine heritage. 

Govern them: and lift them 
up for ever. 

Day by day : we magnify 
thee; 

And we worship thy Name : 
ever world without end. 

Vouchsafe, O Lord: to keep 
us this day without sin. 

O Lord, have mercy upon us : 
have mercy upon us. 

O Lord, let thy mercy light- 
en upon us : as our trust is in 
thee. 

O Lord, in thee have I 
trusted: let me never be con- 
founded. 



292 



CHAP. II. 

ON THE MULTIPLICATION OF PLAIN COPPER PLATES. 

The preparation of plain copper plates, 247. The electrotype plates, 
248. Process for their manufacture, 249. Manipulation 'of the bat- 
tery, ^250. Precipitating trough, 251. Temperature, 262. Positive 
pole, 253. Regulation of the texture of the copper, 254. Single-cell 
apparatus, 255. Time required for the process, 256. Removal of the 
plate, 257. Mode of preparing the plate for engravers, 258. Economy 
in the manufactory, 259. Expense of the plate, 260. 

(247.) The application of the electrotype to the various de- 
partments of engraving is of the greatest importance, 
and the new field open to this branch alone is very extensive. 
Engravings generally are made upon copper-plates which 
have undergone a tedious preparation. The copper which is 
to fae employed for this purpose should be as pure as pos- 
sible ; it has first to be rolled to a certain thickness, after 
which it passes into the hands of the copper-plate maker. 
He carefully examines the plate, and picks out any little 
piece of foreign metal he may chance to perceive, and then 
fills up the gap by dexterously hammering around it, so that 
he draws the neighbouring copper over the hollow. The 
plate is then well hammered, and receives a rough polish by- 
charcoal. The price of a plate so manufactured, is worth 
from two shillings and sixpence to three shillings and six- 
pence per pound. 

(248.) This copper plate is by no means pure, as it gene- 
rally contains tin and other metals which render the en- 
graving sometimes difficult, and the etching very uncertain. 
To obviate these faults we make an electrotype plate on one 
of the prepared copper-plates, and as the metal of this is 






ELECTROTYPE COPPER PLATES FOR ENGRAVING. 293 

absolutely pure it is found to be far- better adapted for the 
purposes of the engraver. This duplicate plate possesses a 
similar surface to the original, and may therefore be at once 
used ; but it is found better to hammer the duplicate, and 
prepare it with charcoal, as that greatly improves it by 
making it more elastic. 

On one of these electrotype plates hammered and prepared 
as plates ordinarily are for engraving, Mr. Palmer had 
various specimens of art executed. First, the plate-maker's 
opinion was taken of it, and he decided that it was vastly 
superior to the common copper ; here we may remark, that 
many persons have doubted whether the electrotype copper 
would bear hammering ; now this plate was thus prepared. 
The plate was then sent to a letter-writer, to receive a 
specimen of this species of engraving, as well as to have his 
opinion of it ; he stated, that the quality of the copper was 
such that much less labour was required for the process 
which it had to undergo. It was then sent to an etcher, and 
he found it greatly superior to ordinary copper-plate ; for 
the nitric acid bit with the utmost uniformity on account of 
the purity of the copper.- A specimen of machine-ruling, 
rose-engine turning, and medal-ruling by Bate's patent ana- 
glyptograph was then executed, and the opinion of all the 
artists concerned in the work was similar ; for the superiority 
of using pure copper over the ordinary copper, which is 
usually contaminated with other metals and charcoal, was 
apparent to all. 

(249.) The exact process by which these electrotype plates 
may be prepared is very simple. The plain plate on which 
the deposit is to take place, is to have a flat band soldered on 
its back, in order that sufficient connexion may be made with 
the zinc of the battery. The heat necessary to effect this, 
drives off the air which infilms the metal, so that if it were 
placed at once in the solution of sulphate of copper the two 
plates would stand a very fair chance of adhering to each 



294 BATTERY, TROUGHS, ETC. 

other. To prevent this serious evil, the plate which has been 
soldered ought to be placed in a cold place for twenty-four 
or more hours, which will enable it to regain a second 
time its film of air. Those who are not skilful in soldering 
metals, may simply place a wire or piece of metal in contact 
with the back of the plate, as that connexion will be amply 
sufficient. Every part of the plate which is not intended to 
receive the deposit, must be covered with tallow, wax, or 
any other non-conducting substance. 

(250.) Having thus prepared the plate, a platinized silver 
battery, which exposes about twice the surface of negative 
metal, is to be charged with dilute sulphuric acid, consisting 
of about one pint of strong sulphuric acid m tw r o gallons of 
water. By using the acid thus diluted, the risk of much 
local action is materially lessened, and for the same reason 
the acid should never be poured into the battery till it is 
quite cold. The best form of battery for these purposes is 
fi.g« 4. The silver has a binding screw soldered to it, and 
a piece of w T ood is fixed on its upper part. The zinc is 
placed on each side of the silver, and consists simply of two 
strips which have no solder attached to them, but are con- 
nected to each other, and to a binding screw by a large screw, 
which embraces at once the two zinc plates and intervening 
piece of wood fastened on to the silver. This very inge- 
nious arrangement appears to have been devised by the 
instrument-maker, from a necessity which the manufacturer 
experienced of repeatedly adding a new zinc as soon as the 
former was dissolved. 

(251.) The precipitating trough may be either the hori- 
zontal or vertical. The vertical trough is an oblong wooden 
vessel cemented in the interior ; on one side the plate to be 
multiplied is placed, on the other a piece of copper to be dis- 
solved (fig. 12.). The horizontal trough is a shallow, square 
vessel, on the bottom of which the plate to be copied is 
placed, and half an inch above it, the copper to be dissolved 



DIFFERENT QUALITIES OF METAL. 295 

(fig. 15.) It is necessary to place the negative plate under- 
neath, or else the uniform strength of the solution would not 
be preserved, but a mass of crystals deposited at the bottom 
of the vessel : or if it is placed in the reverse manner, some 
mechanical means of agitating the solution must be employed. 
The first apparatus is best adapted for a slow precipitation 
and small plates, but the last for a rapid deposition of the 
metal and large plates. 

Whichever process be employed, the trough must be 
filled with a solution of sulphate of copper of a strength 
suitable to the power of the battery. If one battery be used, 
it should consist of a saturated solution of sulphate of copper, 
diluted with rather more than one third of dilute sulphuric 
acid. A solution of nitrate of copper may be employed of 
about one pound to the pint and a half, which will allow the 
deposit to take place more quickly. A nearly saturated 
solution of sulphate of copper may be used, if a series of 
four or five batteries be employed, or the solution be kept at 
a high temperature. It is advisable to place the plate in 
a neutral solution at first, and afterwards, when it is slightly 
covered, in the acidulated solution, in order that the film of 
air may not be removed. 

(252.) Where practicable, the solution should always be 
kept at a moderately high temperature ; as by that means 
the deposit will take place far more rapidly, and the copper 
will be more elastic. The reader must not confound the 
property of elasticity with flexibility, although this is an 
error very commonly made. Flexibility is the property 
which bodies possess of being easily bent ; elasticity is the 
power which bodies have, of returning to their former shape 
after they have been bent. The flexibility of any metal is a 
property very readily* obtained by the laws pointed out > 
elasticity, on the other hand, is a property more difficult for 
the electro- metallurgist to obtain than any other. 

(253.) Having filled the trough with the liquid, we take 



296 REGULATION OF THE QUANTITY OF ELECTRICITY. 

a piece of copper the same size as the plate, and connect it 
by a wire to the silver of the battery. We have now the 
battery charged, the precipitating trough filled with its 
solution, and the piece of copper to be dissolved placed in 
the precipitating trough, and connected with the silver. 
Having proceeded thus far, the wire, soldered on to the 
copper plate on which the new deposit is to take place, 
must be connected with the zinc of the battery, and the 
operator must be particularly careful that dropping the 
copper plate into the precipitating trough is the last opera- 
tion for completing the galvanic circuit, as immediately 
a precipitate of pure copper commences. This does not 
adhere to the copper plate, because it is not in contact with 
it, for a thin layer of atmospheric air is interposed between 
the two. 

(254.) Having put the apparatus in action, the operator 
must regulate the quantity of electricity passing, by ap- 
proximating or increasing the distance between the two 
poles in the precipitating trough, according as he may 
require differences of texture in his copper ; for the reduced 
metal may be obtained soft or hard ; the copper should 
neither be too crystalline nor too flexible, but should be 
of a texture intermediate between both extremes. The laws 
regulating these points have been sufficiently dwelt upon 
above. The apparatus will require no material alteration 
for two or three days, and then the acid in the battery 
should be changed, and the zincs, if necessary, renewed. 
The piece of copper forming the positive pole should always 
be examined, and removed if necessary. A plate should 
not be allowed to remain inactive in a neutral solution for 
any considerable time whilst it is being made, as in that 
case the reduced copper is apt to be in layers. 

(255.) The single-cell apparatus is not at all well adapted 
for making copper plates, because it is impossible to regu- 
late with accuracy the quantity of electricity to the strength 



ECONOMY TO BE PURSUED BY THE MANUFACTURER. 297 

of the solution. In fact all the largest and most perfect 
plates hitherto made have been produced by the battery 
apparatus. 

(256.) The time necessary for the complete formation of 
a plate, varies according to the thickness of the copper 
required, the ease with which the solution suffers decom- 
position, the power of the battery, and the distance between 
the plates in the decomposition cell, or precipitating trough. 
The shortest time in which it could possibly be made, is 
from twenty-four to thirty-six hours ; but with a single cell 
and dilute acid it ordinarily takes a week, or even more ; 
the texture of the copper, however, in both cases, may be 
made similar. The only limit which is afforded to the 
rapidity of the process, is the cupreous salt. As the 
nitrate is the most soluble salt of copper, we never can 
obtain a plate more rapidly than the strength of its solution 
will allow. 

(257.) Having made the plate, we have now to take it 
off; and for this purpose, any copper embracing the edge of 
the original plate is to be removed ; after which, the 
operator without any difficulty may separate the two plates, 
for provided he has followed exactly the directions which I 
have before given for insuring a film of air on the plate, not 
the slightest adhesion will exist. 

(258.) A plain copper plate is thus made, which can be 
used at once by the engraver, or it may be hammered and 
rubbed with charcoal, as copper plates ordinarily are. Du- 
plicate copper plates have been made from another similar 
plate, but we can obtain a copper plate from smooth sub- 
stances, which are not capable of being acted upon by the 
fluid ; thus, smooth white wax, sealing wax, or smooth 
plaster of Paris, will receive the deposit after they have 
been black-leaded. 

(259.) The manufacturer who makes electrotype plates in 
an extensive way, must endeavour to lessen the expense of 



298 USE OF THE SULPHATE OF IRON, COPPER CLIPPINGS. 

the process by every possible means. In the first place, he 
must recollect that the mercury used for the amalgamation 
of the zinc is not at all acted upon, but that when all the 
zinc is dissolved, it remains upon the fine particles of foreign 
metals which the zinc contained. He should carefully 
preserve this mass, as well as all the fragments which have 
been left ; the mercury may in a great part be separated 
from this, by enclosing the mass in wash-leather and 
squeezing it ; the rest may then be obtained by distilling 
the residue. Theoretically, the operator ought to regain as 
much mercury as he originally employed ; but practically 
he will always suffer a certain loss. 

The sulphate of zinc left in the battery after it has been 
exhausted is absolutely pure; and therefore the solution 
may be evaporated and the crystals of the sulphate of zinc 
obtained ; or the metal may be converted into a carbonate, 
for which there is a great demand in the arts. The deposited 
copper in the same manner is also pure, and, therefore, all 
the clippings should be preserved for the purpose of alloying 
gold, as it is necessary to have a perfectly pure metal for 
that purpose ; but strangely enough a refiner told me that he 
did not approve of electrotype copper for his purposes. 

Those who manufacture a great number of plates and to 
whom time is not an object in their proceedings, can adopt 
a peculiar form of battery. The battery should be large, 
and should be connected, not to one precipitating trough 
alone, but to a series arranged exactly as a compound bat- 
tery ; thus, if twenty troughs were arranged and connected 
with the battery, they would obtain twenty pounds of 
copper for one pound of zinc dissolved. The solution of 
sulphate of copper in each cell should be rather more 
dilute, and be much more acid than when a single trough 
is employed, and the positive copper-plate and negative 
plate of each cell should be of the same size. The large 
battery, in this case, is not attended with more expense 



EXPENSE OF THE PROCESS. 299 

than a small one ; for to do any given amount of work, as 
much zinc would be dissolved in a battery made of a silver 
thimble, as in one exposing a surface of negative metal 
equal to the surface of the whole of Europe ! The rationale 
of this apparent paradox is explicable by the important law, 
that "In every cell the amount of chemical action is the 
same;" one battery will therefore, for every pound of zinc 
dissolved, precipitate one pound of copper in each precipi- 
tating trough, so that the number of precipitating troughs, 
arranged as a compound series, will give the number of 
pounds of copper thrown down for each pound of zinc dis- 
solved. If we consult the equations given in a former part 
of this work, we shall find that it is of no use increasing our 
batteries above a certain size, and therefore we must take 
care to lessen the resistances in all our troughs. 

(260.) In this great commercial city it is useless to men- 
tion the excellence of the process, unless, at the same time, 
some idea be given of the expense attending its adoption. 
This, with a single battery and precipitating,.trough, will be, 
first, the intrinsic value of the copper, say one shilling and 
twopence for each pound, plus an equivalent of amalgamated 
zinc one shilling, plus some zinc lost by local action, plus 
sulphuric acid, say fourpence, equal to two shillings and 
sixpence a pound for the bare cost of the materials. To 
this, labour, time, house rent, and profit are to be added, 
which will increase, .at present, the price to one sovereign 
per pound of copper ; though doubtless the expense will be 
diminished as the demand increases. For plain plates 
persons would hardly like to give this price, unless an en- 
graver were about to execute a very splendid subject, and 
then perhaps it would be fully worth his while to go to the 
extra expense, from the superiority of his materials. 



300 



CHAP. III. 



ON COPYING ENGRAVED COPPER-PLATES. 






Engraved copper-plates, 261. Design on the plates, 262. Various kinds 
of engraving, 263. Uses of engraved plates, 264; for the potteries, 
265 ; for calico printers, 266. 

(261.) Engraved copper-plates are not more difficult to 
copy than plain ones. A plate possessing the most elaborate 
design, the most brilliant conception, the finest execution, the 
most delicate workmanship, in fact everything calculated to 
render a plate valuable, can be copied with the same readi- 
ness, the same fidelity, the same ease, as the plate without 
any workmanship at all ; because the deposit of new metal 
takes place in such a way that an exact cast is made in both 
instances. 

(262.) The design of all engraved copper-plates is in 
intaglio or depressed below the surface, and the problem is 
to obtain a duplicate in a similar state. To effect this, a 
reverse of the plate must first be taken in relief. This may 
be done in various ways. In the first place, a relievo may 
be obtained in copper, precisely in the .same way as a dupli- 
cate plain plate. (249—257.) This is the most perfect 
process, and should always be adopted for very delicate 
designs. 

An impression of a plate may be made on perfectly clean 
lead, by placing the lead on a printing-press with an iron 
bottom, and then placing the engraved plate upon the top of 
it. The two are then to be run through the press, exactly 
in the same way as an ordinary print is taken off. In this 
operation, if the lead be placed underneath, a very perfect 



RELIEVO MOULD OF ENGRAVED PLATE. 301 

impression may be effected ; but the upper plate is sure to 
become bent, which is a disadvantage. If the copper- plate 
is placed underneath, that will receive no injury, but the lead 
will be curled in a similar manner. Now, on considering 
these facts it occurred to me, that if a third plate above the 
other two were employed, there would be no curling, and 
upon the experiment being tried two or three times, my 
expectations were realized, for neither lead nor copper were 
curled to any amount. The mode in which I directed the 
experiments to be performed, was to place smooth lead at 
the bottom, then the copper-plate upon this, and lastly a 
third metallic plate at the top, which became curled by the 
process. A great disadvantage, however, in the use of 
lead for this purpose is, that the metal is liable to stretch 
unequally. 

A perfect mould may be taken from an engraved plate in 
white wax, but it requires some practice to copy a large 
# plate. The white wax must be black-leaded, and then 
placed in the solution. Plaster of Paris may also be used to 
take a relievo impression, and the stereotypers are very ex- 
cellent hands at using this substance ; but although I have 
made duplicate copper-plates from plaster, I am afraid that 
it will scarcely be thought sufficiently perfect to be used for 
the electrotype in all cases. The plaster must be very 
carefully filled by the methods I have elsewhere detailed, 
and after the application of the black-lead it may be placed 
in the solution. 

A tolerably perfect matrix may be made with gutta 
percha, and I have reason to believe that some operators 
have a secret process for forming it, which at present they 
decline to put me in possession of. 

Having by any one of these methods taken a relievo im- 
pression, a reverse is again to be taken, in a manner similar 
to that pointed out for copying a plain plate. The film of 
air, which substances acquire by exposure to the atmosphere, 



302 DIFFERENT KINDS OF ENGRAVED PLATES. 

must be obtained before a metallic matrix is placed in the 
solution. (249—257.) 

(263.) The back of the reduced plate will be always more 
or less rough, which is to be filed smooth before a print is 
taken from it. Sometimes, when the plate is thin, a second 
plate of tin or iron is soldered into the back ; but the unequal 
expansion of the metals, when heated, is liable to be attended 
with inconvenience. By the use of this artificial back, how- 
ever, we can employ the crystalline copper, which is so in- 
tensely hard, that in all probability the plate would last 
much longer. 

The front of the plate is liable to exhibit over its other- 
wise polished surface an appearance in copper, as if the 
slightest breath, or film, covered the surface. This has been 
technically termed u the curd," and is instantly removed by 
the copper-plate maker by a few slight touches with his 
charcoal. To account for this curd will not require much 
thought when we mention^ that if the operator simply places 
his finger on a polished plate the copper reduced upon it 
would have precisely similar marks ; and I have seen it ex- 
hibit every line of the finger, and even the opening of each 
perspiratory duct. 

(264.) Those not much acquainted with engraving will 
perhaps be astonished at the various means which artists 
employ to execute an engraving. They may however be 
divided generally into three heads. The first contains those 
cases where the design is made by instruments of various 
kinds, as gravers, dry points, &c. In the second, the device 
is obtained by acting partially on the plate by acids capable 
of dissolving it, or in fact by biting out the lines or figure of 
which the engraving is constituted. The third kind, where 
the surface of a plate is uniformly raised up by an instrument, 
in such a way that it prints all over perfectly black, in which 
state it is ready for the engraver. By burnishing the plate 
all the asperities are rubbed off, and that portion thus treated 



USE OF ENGRAVED PLATES. 303 

prints whiter : so that by regulating the degree of bur- 
nishing the different effects of light and shade are produced, 
which constitute the engraving. This is called rnezzotinto. 
It is far cheaper than the line engraving, and is now much 
m vogue. Each of these three classes of engraving has 
been copied by Mr. Palmer and others, with the utmost 
fidelity, so that the application of the electrotype may be said 
to meet every case for which it is likely to be required. 

The Art Union of London have used electro-metallurgy for 
their purposes. Ten different original plates were multiplied 
in this manner. In answer to an application on my behalf, 
the secretary stated that the impressions taken from each elec- 
trotype plate varied from 400 to 1000, depending chiefly on 
I the character of the engraving, the average being about 720. 
They found that repairing was required to some extent in 
the earlier plates, but latterly it was only necessary where 
the plates were much undercut or burnished. The council 
of the society consider that for large numbers of impressions 
more dependence can be placed on steel plates if carefully 
watched while at press, than on plates produced by the elec- 
trotype. 

(265.) Engraved plates were not employed till the four- 
teenth century, but now their uses are manifold. To hand 
down to posterity, and to diffuse among the multitude, copies 
of the choicest pictures and other works of art, are their 
most prominent applications. To perpetuate the resem- 
blance, and to distribute the portraits of the great, the good, 
and the beloved, are other important uses. With these the 
public are most acquainted, but they do not constitute a tithe 
of the purposes for which engraved plates are required. 
The great consumption now for these plates is at the pot- 
teries ; for almost every common dinner-service, or every 
piece of pottery, has its design given by a copper plate. 
The device is deeply cut in the copper, and then it is printed 
on a piece of thin paper ; but the impression is printed with 



304 USE OF ENGRAVED PLATES. 

a composition of arsenite of cobalt instead of the ordinary- 
ink. The paper is then pressed upon the pottery plate 
before it is glazed, in order that the ink may adhere to it ; 
after which the paper is carefully washed off. The pottery 
plate is next glazed, and is then ready for use. 

The most unmeaning devices are printed on the plates; 
and the willow and other similar patterns certainly exhibit 
no great beauty of design. Our common pottery-ware, how- 
ever, is the envy of every foreign country, for nowhere but in 
Britain have they ever been able to make common earthen- 
ware with any degree of perfection. The electrotype pro- 
mises to materially improve the patterns of our otherwise 
unrivalled pottery, for the expense of engraving valuable 
plates has been hitherto such, that on account of the small 
number of copies they will afterwards print their application 
has been necessarily prevented. Now if a plate cost originally 
a thousand guineas, an infinite number of duplicates could be 
taken from it by the electrotype, and in this way the expense 
of every common dinner plate would be the same, whether 
the ordinary blue-and-white service were used, or plates and 
dishes were embellished with copies of our finest works 
of art, the most exquisite scenes of nature, the most elaborate 
machinations of fancy, or the most intricate specimens of 
execution. Before long I trust that the silly devices we 
have at present in use, will be changed for more elegant and 
highly finished drawings. 

(266.) A second extensive application of copper plates, is 
to be found in the manufactories of the calico-printers. They 
employ copper plates for printing their calicoes. In these 
instances, the copper plate is first engraved, and bent round 
so as to form a cylindrical roller, and then the two edges are 
soldered. By contrivances the die is placed by other rollers 
into the hollow of the engraving, when the calico to be 
printed passes under the roller by the force which the roller 
itself exerts from the revolution imparted to it by a steam- 



MULTIPLICATION OF ENGRAVED PLATES. 305 

engine. In this way twenty or thirty yards of calico can be 
printed in a few minutes. These copper plates might be 
either multiplied before they are bent, or afterwards, upon 
the same principles that plain electrotype copper plates are 
made. There would be no great difficulty to make a perfect 
copper roller without any solder, should that be a desideratum 
to the manufacturer. 

By the kindness and courtesy of Captain Yalland, R. 1ST., I 
was enabled to examine the mode in which the multiplication 
of engraved plates is usefully carried out at the Ordnance 
Map Department, at Southampton. The plans of the maps 
are first drawn upon paper, from which the engravers work. 
There are many curious plans by which labour is saved by 
mechanical contrivances ; as some effects are produced by 
fine lines, others by dots. Again the representations of 
words are engraved mechanically, and the altitudes of different 
places are punched into the copper plate. These copper plates 
are of large size, and are technically called double elephant 
plates, and when finished are transferred to the electrotype 
department, where Mr. Geddes has arranged and conducts the 
process in a masterly manner. The batteries are of plati- 
nized plated copper, the back and edges being very thoroughly 
varnished to prevent any action from the liquor. The pieces 
of plated copper are carefully screwed on to a frame, so that 
one piece of zinc can radiate, to each surface of negative 
metal. In a former part of this work I have recommended 
large troughs, but what will my readers say to troughs of 
such depth and magnitude that the dilute sulphuric acid will 
last for nearly two years before it becomes exhausted with 
zinc ; and there can be no doubt but that these large troughs 
are practically economical and convenient. The zincs are 
large cast plates, which are thoroughly amalgamated ; and 
they inform me that since they have commenced operations 
they have used about 320 pounds of mercury, some of 
which, however, is still reclaimable by distilling the frag- 

15 



306 MULTIPLICATION OF ENGRAVED PLATES. 






ments of zinc* remaining undissolved. The precipitating 
troughs are horizontal, and each is placed upon four wheels 
for convenience of moving it about. The positive pole is 
made of a very thick plate of copper which is placed at the 
bottom of the vessel, and the plate to be copied is fixed 
firmly to a piece of wood, which comes within a short dis- 
tance in contact with the positive plate. The solution is 
rather diluted, inasmuch as this form of apparatus demands a 
somewhat slow deposit. 

The object in placing the negative plate at top is to pre- 
vent any foreign body from falling upon the plate, and thus 
injuring the duplicate ; but this course would insure a bad 
deposit of metal, if some contrivance were not used to circu- 
late the fluid and cause a proper diffusion of the metallic 
salt continually formed at the positive pole. To effect this 
result, the whole trough is alternately raised up on one side 
and then on the opposite, which causes a little splash each 
time. This effect is produced by mechanical contrivances 
attached to the steam engine, and appears to answer ad- 
mirably. 

Great care is taken to have a pure solution of sulphate of 
copper, with dilute acid and water, and the positive pole is 
frequently cleansed of that black powder which is always 
left upon it. 

The rate of deposit in this horizontal apparatus where the 
negative plate is uppermost, must be necessarily slow, but it 
is stated that from one and a half to two pounds of copper 
were deposited upon a double elephant plate every day. 

Captain Yalland informed me that by making connection 
the instant the negative plate was inserted in the liquid they 

• According to Mr. Warren De la Rue, 1000 parts of zinc plate 
residues usually give the following results, on analysis : — zinc, 673, 
mercury 43, loss 284. From the distilled residue a very remarkable 
crystalline compound was obtained of the form of right rhombic prisms, 
and appeared to obey the following formula : — 240 zinc, 8 iron, 5 lead, 
and 4 copper „ 



MULTIPLICATION OF COPPER PLATES. 307 

had never encountered a single mishap by the adhesion of 
the new plate. 

Electro-metallurgy has, in this case, been of the utmost 
importance, by enabling the ordnance maps to be published 
at a moderate price ; but this is by no means the only bene- 
fit which it confers on the public. The Ordnance maps 
represent the entire surface of England, and every spot on 
these maps represents some definite spot in existence. But 
the objects in each spot in a series of years change ; a church 
is built upon the site of a tree ; railroads are made over 
rivers and through woods. Now, to accomplish these 
changes, the electrotype is of great value, for it is only 
necessary to form a matrix from the original plate when the 
engraved parts appear in relief. Wherever any alteration 
is desired these projections are scraped off. A duplicate 
plate is again made, when the parts to be altered are flat and 
suitable to go into the hands of the engraver to have the 
alteration inserted in the plate. In this manner three sets 
of plates have been produced from each original, each being 
different from the other. 

Notwithstanding all this perfection of detail, it appears 
to me that ultimately it will be found preferable to make a 
complete series of blocks for surface printing in addition to 
those plates which have been already prepared, as that course 
will reduce the price of printed maps to at least one fourth 
their present cost; a matter of no small desideratum to the 
multitude to whom the cost is a great object. 

The unlimited multiplication of copper plates by electro- 
metallurgy opens a question of curious interest ; for however 
beautiful the design of any work may be, however perfect 
its execution, if it is always before our eyes it ceases to 
have a pleasing effect. Who ever saw a ploughman ad- 
miring the brilliant petals of a buttercup, and yet what work 
of art is equal to it ? In this case, however, the object is 
far more common than any work of art possibly could be- 



308 REPRODUCTION OF OLD ENGRAVINGS. 

come, and, therefore, probably but little analogy exists 
between the two cases. Those print-sellers who allow but 
a limited number of any engraving to enter the market act 
foolishly ; for, if the design is really excellent, it would be 
impossible to render it so common that every individual in 
the whole range of civilized nations should cease to admire 
it. The more perfect the work the greater extension will it 
bear ; therefore, let those who engage in these arts seek rather 
to produce a perfect work and an extended circulation, than 
several imperfect engravings with but limited circulation. 
Engravers who are desirous of obtaining not only the neces- 
sary means for present subsistence, but also a laudable and 
permanent reputation, should cause a relievo of their work to 
be executed and deposited in some national collection, as 
with but moderate care such a cast would last from genera- 
tion to generation. 

Mr. Russell has discovered a process by which a steel 
plate can be prepared from a single impression. He keeps 
this process at present secret; he tells me that he has worked 
it out with little or no knowledge of chemistry. After the 
plate is prepared, he states that it generally requires to be 
touched up by the graver in some parts, and that the total 
charge is about five shillings per square inch. He himself 
considers that his method will enable fine old engravings to be 
brought within the range of the means of the middle classes, 
and he entirely repudiates the vending of these duplicate 
plates as originals, although there is too much reason to fear 
that such a course is extensively practised. I recently 
purchased a proof engraving of the Village Politicians for 
eighteen shillings, whilst the original is worth fifteen or 
more guineas. Although critical judges must determine 
that the duplicate is vastly inferior to the original, yet the 
impression gives a pleasing picture. According to ordinary 
notions of trade profits, my picture should not have exceeded 
five or six shillings. 



METHOD OF OBTAINING IMPRESSIONS FROM ENGRAVINGS. 309 

Poitevin has described a method by which we may 
obtain on plates raised or sunk impressions, from drawings 
or engravings : these plates, in their turn, may be used for 
multiplying the impressions. The engraving is exposed to 
iodine vapours, which only adhere to the black parts ; the 
sheet is then attached to a silver plate, polished according to 
Daguerre's method, by means of slight pressure ; the iodine 
is transferred to the silver, so that layers of iodide of silver 
are formed corresponding to the shadows of the engraving. 
The plate is then immersed into a concentrated solution of 
sulphate of copper, and used as the negative pole of a weak 
battery ; it is removed before the iodized portions are coated 
with copper. The plate is at once washed, and the iodide 
removed by hyposulphite of soda ; the copper surfaces are 
then oxydized by heat until they become dark brown, the 
exposed silver surfaces are amalgamated after cooling, and 
the plate being covered with two or three layers of gold 
leaf the mercury is volatilized by heat. The gold is brushed 
off from those parts which are covered with oxyde of copper, 
and to which it does not adhere. The oxyde of copper is 
then dissolved by a solution of nitrate of silver, and the 
silver, as well as the subjacent copper, exposed to the action 
of dilute nitric acid. The parts covered with gold are not 
affected, so that the etching may be carried to any depth ; 
the plate which is thus obtained, may be employed for taking 
impressions, in the manner in which wood-blocks are used. 

In order to obtain plates engraved as deeply as the plates 
used for ordinary copper-plate engravings, a plate of gilt 
copper is employed. By proceeding as above, the light 
parts are covered with copper, and the shaded parts being 
deprived of the iodine, the gold amalgamated is removed 
from the shaded, and the oxyde of copper from the light 
parts by acid. The latter will then be protected against the 
further action of the acid by the gold, and we obtain a deep 
engraving. 



310 



CHAP. IV. 

ON THE MULTIPLICATION OF STEEL PLATES. 

Process for making a copper plate from a steel one, 267. Perkins's appa- 
ratus, 268. Comparison between the two processes, 269. 

(267.) Steel plates can only be copied in a peculiar man- 
ner. They must not be placed either in the sulphate, nitrate, 
or muriate of copper, as certain destruction would ensue. 
I have heard of steel plates being thus destroyed, and 
therefore I particularly dwell on the fact to prevent its 
repetition. The crystallized acetate of copper is not decom- 
posed by steel, though after the galvanic current has been 
passing for some time free acid is left, which is apt to attack 
the steel. A steel plate, however, undergoes no change in 
an alkaline ammoniuret of copper, ammonio-sulphate, or 
ammonio-nitrate of copper. From these salts, therefore, 
the copper may be thrown down upon the steel, but I am 
afraid that no advantage can be taken of the fact, as the 
reduction of copper by these means is attended with con- 
siderable difficulty. Under these circumstances, we must 
have recourse to other methods of making a relievo duplicate 
from a primary plate of steel. This may be done in either 
lead, gutta percha, wax, plaster, or any other substance on 
which we can obtain a perfect cast, and from this a copper 
plate can be again made in the same way. 

Besides these modes of making a relievo from a steel 
engraved plate, I have yet another plan to propose, which is 
even far superior to any yet detailed, and which on that 
account must supersede every other mode. This process of 
multiplication, which is so excellent, consists in first making 



MULTIPLICATION OF STEEL PLATES. 311 

a reverse in silver, and lastly, a second reverse in copper, 
which is used at once for printing. To effect this object, the 
steel plate must be carefully cleaned from any adherent 
grease, and allowed to remain in a cold place twenty -four 
hours before using it. A strong solution of argento-cyanide 
of potassium must then be procured, and placed in a stone- 
ware or glass vessel. A piece of silver connected with the 
platinized silver of a battery should be next placed in the 
solution, and the size should be about the same as that of the 
steel plate. The last operation is to immerse the steel plate 
itself, which must not be effected before it is connected with 
the zinc of the battery. The process should be continued 
till the silver is sufficiently thick for removal, which opera- 
tion must be performed in the usual manner. There are, 
perhaps, no processes in the whole range of electro-metallurgy 
more easy than this ; for the silver may be obtained of ex- 
cellent quality, and not the slightest adhesion will be found 
to exist between the original and duplicate ; even the absolute 
polish of a highly burnished surface will not suffer any 
injury from such a proceeding. 

It is hardly necessary to mention that this process is ap- 
plicable to steel dies, punches, and every other kind of 
article, as no greater difficulty would ensue in conducting 
the operation. 

The only detriment to the formation of a silver relievo, is 
the expense of the metal, which in large plates would be con- 
siderable ; perhaps, in some cases, that might be diminished 
by giving a layer of copper ; otherwise we must be careful, 
as soon as we have formed a second reverse of copper, 
to re-melt our silver, and take especial care to suffer as little 
waste of metal as possible. The process, except in the great 
value of the silver, is profitable from the equivalent of silver 
being high. 

(268.) Before I bring to a conclusion a description of the 
method by which duplicate copper plates can be obtained 



312 Perkins's process, 

from primary plates either of steel or copper, I think it 
necessary to mention, that metallic plates may be multiplied 
not only by voltaic, but also by mechanical means. This 
latter method has been in use for some years, and was 
devised by that original mechanic, Mr. Perkins, who obtained 
a patent for his invention. The apparatus he employed may 
be described generally in a few words : he first engraves on 
soft steel plates, and then hardens them. From the intaglio 
impression of the device he obtains a relievo impression on a 
circular roller of soft steel, by employing an immense pressure 
on the roller as it revolves. The circular roller which has 
the drawing in relievo is then hardened, when any given 
number of printing plates can be made from it, in a very 
short space of time, by placing a plain plate under the roller, 
and causing the roller to revolve whilst under an immense 
pressure. 

Some difficulty arises in performing the operation, for if it 
is continued too long, the fine work is injured ; if too short 
a time, the deep portions are not sufficiently indented. 

(269.) The duplicates by Mr. Perkins's process are never 
such perfect copies of the original but that engravers can 
tell one from the other, on account of an apparent imperfec- 
tion in the plate, which requires the plate to be touched up. 
It is needless to add, that this immediately destroys absolute 
identity. The duplicate obtained by electricity is perfectly 
identical with the original plate, and no engraver can tell the 
original when both are placed before him. However, there 
is one circumstance which is very singular, namely, that the 
duplicate or second plate gives a more beautiful impression 
than the original. The variation does not arise from any 
difference of tint, for this depends more on the printer than 
the plate, and is technically termed the pull. In fact, a 
copper-plate printer can print the same plate of several de- 
grees of shade, depending upon the quantity of ink which he 
leaves in the work. The beauty of the duplicate over the 



DURABILITY OF STEEL PLATES. 313 

original, perhaps, is to be attributed to the superior quality 
of the copper, which gives a better tone to the impression, for 
certain it is that every electrotype is slightly superior to the 
original plate. To give an idea of the durability of steel 
plates for printing, I may mention that Mr. Oldham, the 
Bank Engineer, informs me that a steel plate, with occa- 
sional reparation, will print about 60,000 impressions. 

Some years ago an attempt was made to print from stereo- 
type copies of engraved plates. A plaster cast was made 
from the original, when a stereotype copy was formed in the 
usual manner ; but the process failed, not from a want of ac- 
curacy in the duplicate, but from the circumstance that the 
alloy of lead was found not to print clear like the copper or 
steel originals. 

Since this edition has been at press, it has occurred to me 
that for all multiplications of plates it would be preferable to 
use a copper pole made like a Venetian blind, each blade 
being about three inches in depth, and inclined at an angle 
of 45° to the perpendicular, and the blades being separated 
from each other by an interval of half an inch. By this 
plan the deposit may be more rapidly carried on ; but at 
present I have not had time to ascertain, on an extensive 
scale, its superiority over the present plan. 



15* 



314 



CHAP. V. 

ON THE MULTIPLICATION OF WOOD-CUTS. 
Design on wood-cuts, 270. Process, 271. Conclusion, 272. 

(270.) Civilised nations ought to regard the first application 
of wood-cuts with peculiar veneration, as they seem to have 
suggested the idea of printing. At the present time, how- 
ever, wood-cuts deserve especial notice, on account of the 
beauty of their execution; for they have now been brought 
to such perfection, that in minuteness and sharpness of draw- 
ing, I have seen specimens which fairly equal steel en- 
gravings. They might appear not often to require multipli- 
cation, because it is almost impossible to wear them out; 
10,000, 20,000, 50,000, nay, even 500,000 or more impres- 
sions have been taken from one wood block. Still, however, 
a duplicate in copper is frequently required for various 
purposes. Wood-cuts are somewhat the reverse of copper- 
plates ; for in the latter, the print is obtained from the ink 
left in the hollows of the plate, but in the former the design 
is the most elevated part, and the impression is printed from 
the ridges. 

(271.) Surface printing seems to have been very little 
employed till the fifteenth century, at the conclusion of 
which it reached a high style of perfection, the cuts of 
Albert Durer, as well as those of his contemporaries, being 
much esteemed for the beauty of their design and execution. 
After that period the art began, strange to say, again gra- 
dually to decline, and was nearly lost, when the genius of 
Bewick, at the conclusion of the eighteenth century, gave 
a fresh stimulus to this important branch of art, and from 
that period it rose to its present unrivalled excellence. The 



SURFACE PRINTING. 



315 



superiority of surface over other kinds of printing depends 
upon the facility with which the former operation of print- 
ing is performed, and the comparative indestructibility of 
the design. 

For the multiplication of wood-cuts and other analogous 
designs for printing surface blocks, electro-metallurgy is 
useful in many ways. For cuts that are used for a variety 
of purposes, as the arms of the sovereign, where many 
persons design a separate block to print, the type-founder 
usually has the design cut in wood. This is coated at the 
back and edges with wax or grease, black-leaded, and im- 
mersed in the solution of copper in the usual way, so that 
an intaglio copper mould is produced. This mould may be 
used to make copper reverses, which are at once ready for 
the printer ; or it may be used as a die to form cliche e casts. 

In many instances, especially from moderate-sized wood- 
cuts, a cliche e reverse is at once taken from the cut. At 
present there are few in England that are trusted with the 
performance of this operation, and I believe that only 



Fig. 37. 




Branston practises it as a profession. From the annexed 
cut, designed by the younger Landseer, then a lad twelve 



316 MULTIPLICATION OF WOOD-CUTS. 

years of age, whose rising genius will doubtless some day 
place him at the top of his* profession, a clichee mould was 
first taken, and then, from the clichee, an electrotype 
duplicate, which, as in every case where an electrotype is 
wanted for surface-printing, required the back to be coated 
with solder, or fastened to a block of wood to render it thick 
enough for fixing with the other type. The above cut I am 
enabled to give through the kindness of Mr. Longman ; the 
clichee was executed by Branston, and the electrotype by 
De la Rue. Valuable wood-cuts, however, are but seldom 
permitted to have clichees taken from them, for fear any 
mischance or injury should ensue to the original. In these 
cases, a reverse of the original is formed in gutta percha, 
plaster, white wax, &c. ; the former, however, being much 
to be preferred. Mr. De la Rue has discovered and recorded 
that electrotypes will not long print vermilion inks, although 
ordinary copper is well adapted for that object. The electro- 
type after some time decomposes the vermilion and turns 
white, showing that it has reduced the mercury. This fact 
he attributes with great probability to a difference of aggre- 
gation of the two metals. 

The multiplication of wood-cuts has been far more exten- 
sively carried on by Messrs. De la Rue than by any other 
firm. Their manufactory is reckoned, by those most com- 
petent to form an opinion, one of the most complete speci- 
mens of the union of art and science in mechanics, physics, 
and chemistry, that this metropolis, or perhaps even the 
entire world, can boast. The electrotype department occupies 
but a trifling nook in their vast establishment, and is used 
for the multiplication of the surfaces they employ for print- 
ing. Engaged extensively in the printing of every kind of 
ornamental and fancy stationery, they have a vast number 
of designs they find convenient to multiply by the electrotype, 
find, perhaps at their establishment the value of electro- 



SURFACE PRINTING FROM COPPER. 317 

metallurgy in the department of surface-printing is better 
seen than at any other manufactory. 

Electrotypes for surface-printing are found to be even pre- 
ferable to the wood itself, as not only is the copper far more 
durable than the wood, but even the cupreous surface is 
found to print more beautifully. 

Our friend Punch finds a copper face is suitable for his 
purposes, inasmuch as his title-page is electrotyped. Every 
body reads Punch, and likes to see every person's follies 
shown up in a humourous point of view except his own ; but 
his turn coming but seldom he is perfectly satisfied to enjoy a 
laugh at other people, notwithstanding the occasional sacrifice 
of himself. From the artistic and literary talent employed 
upon this periodical a very large sale is secured, and I am 
informed that between four and five millions of impressions 
have been taken from their frontispiece, which well shows 
how far a coppered face will serve, at any rate for surface- 
printing. As Punch has amused his readers at my expense, 
he cannot complain at my endeavour to instruct mine 
at his. 

I am also informed that the vignette at the top of the Illus- 
trated London News is engraved on copper to print as a 
wood-engraving. This wonderful periodical, which has done 
so much for the public in wood-engraving, has also an enor- 
mous sale ; for nobody is satisfied without seeing the represen- 
tation of every occurrence which takes place, and it is said 
that some copies of this vignette have printed at least three 
millions of impressions. Doubtless this journal would find 
the electrotype suit their purposes as well as the copper die. 
It is a curious fact that at the present time the great diffi- 
culty which is experienced by the large periodicals is, that of 
getting them printed to supply the public. The Times 
newspaper has been so much inconvenienced that a new 
printing press has been devised to meet the difficulty, and 



318 applegarth's printing machine. 

even the weekly journals experience great trouble on this 
score, and can only supply to the venders the few quires as 
they come from the press. The demand for newspapers 
continually increases with improved intelligence, so much so 
that the aid of the mechanic is perpetually being sought to 
meet the increasing wants of the public, and in some cases 
the printer is compelled to work with two sets of type. 

The present machine for printing the Times newspaper, 
devised by Applegarth, is an astounding example of human 
ingenuity. It is a great object to be able to print one side 
of the. paper as rapidly as possible, so that the public may be 
supplied with intelligence up to the latest possible moment. 
The type is set up in columns as for any other newspaper, 
but, instead of lying flat, is fixed on a cylinder with a wedge- 
shaped rule between each column to adapt the series of flat 
surfaces to the circular form of the cylinder. As the cylinder 
is placed vertically the type requires to be screwed very 
tightly, otherwise it might be disarranged by centrifugal 
force, or other causes, during the action of the machine. By 
elaborate contrivances of wheels and tapes it is so arranged 
that during one revolution of the cylinder the type is inked 
by machinery, and supplied by eight men with eight sheets 
of paper, which are printed, and removed by eight other 
men. By this mechanism 10,000 impressions are printed 
per hour, forming a strong contrast with the old mode of 
printing by hand-presses in vogue at the beginning of this 
century. 

During the action of the machine every paper must be 
supplied precisely at the right time, otherwise it would not 
be printed at the right place ; and much of the nicety of the 
machine is given by care movements, which regulate the 
speed, of different parts of the operation. It is perfectly 
bewildering to see the machine in motion, the rapidity with 
w r hich the sheets traverse is extraordinary, and whether we 
consider the machine for the effort of mind required in its 



Baxter's colour printing. 319 

construction, or whether we consider it for the social and 
moral results which it produces in the community, we must 
admit that it is a far more noble testimony to the power and 
ingenuity of this country, than the pyramids were to Egypt, 
or St. Peter's to Rome. 

A process devised by Baxter is now much in vogue. He 
is said to employ a copper or steel plate to give the general 
outline. Subsequently he engraves one or more wood blocks, 
which he dabs with different coloured varnishes instead of 
printing-ink, and in some cases he is said to apply one 
colour over the other • and then the print is taken from a 
press as from an ordinary wood-cut. By the combination of 
about eight colours all the beautiful artistic effects can be 
produced. By Mr. Baxter's processes the various tints blend 
into each other in succession, and thus character is given to 
the figures, and a degree of tone and shading is given to 
the landscape. The appreciation of these pictures by the 
public is interesting ; and I have authority for stating that 
some have reached a sale of 300,000 copies ; and thus, by 
placing elaborate and beautiful paintings within the means of 
the industrial classes, the taste of the community cannot fail 
to be improved. From the incredible sale, the first cost of 
getting up is of no object, and I am informed the actual 
working of the smaller subjects is slightly under half a 
farthing each. The coronation of her Majesty is the most 
elaborate work which he has executed ; but a holy family 
after a picture in the possession of Lord Brougham, a 
portrait of Jetty Treffs, and other specimens now lying before 
me, are very beautiful examples of this style of art. Doubt- 
less the electrotype, by allowing us to vary the details of an 
original block in any number of duplicates, might be brought 
to great use for Baxter's process. In my visitations in more 
humble dwellings I like to see these pictures. They enliven 
the homes of those whose duties have occupied the day. 
The beautiful forms and harmonious colours gladden the 



320 GLYPHOGRAPHY. 

heart of the owner, and thus we find that science contributes 
to morality and happiness. The English, as a nation, are 
remarkable for their non-appreciation of the harmony of 
colours ; and doubtless printed pictures, if extensively circu- 
lated, cannot fail to tend to remedy this defect. 

Electro-metallurgy promises to lend an important aid for 
printing surfaces generally, as an unlimited production will 
allow of the use of illuminated letters similar to those which 
graced the works of former years. There is but one 
obstacle to a great improvement in this department of the 
arts by electro-metallurgy, and that is the insecurity which 
the founder experiences in the absolute right to his pro- 
ductions ; for if he incurs a great expense and executes a 
splendid design, as soon as he sells a duplicate he is liable 
to have the design pirated, when perhaps his original out- 
lay will not be sufficiently covered. As soon, however, as 
more stringent laws are made to protect particular designs 
every printed book will doubtless show the benefit of electro- 
metallurgy. 

One of the most beautiful series of specimens of printing 
from electrotypes is to be found in an illustrated edition of 
Thomson's Seasons, all the woodcuts of which were care- 
fully preserved, and the actual printing performed from 
electrotype-copies. (Jig. 38.) 

In no application of electro-metallurgy is the value of the 
science more conspicuously shown than in a mode of pro- 
ducing surfaces for printing lately patented and called by 
the patentee Glyphography. This branch of art was in- 
vented by Mr. E. Palmer, of Newgate Street, and forms an 
important feature for the general illustration of printed 
works, and on that account demands particular consideration. 
The term Glyphography has been given by Palmer to this 
invention, to signify that the original drawing itself is at 
once engraved, requiring no copying, and in fact scarcely 
any instruments, except those with which the artist makes 



GLYPHOGRA 



321 




Fig. 38. 

his design. The mode in which so extraordinary an end is 
accomplished, appears ridiculously simple when it is detailed. 
The most essential part of the process is to make all the 
surfaces for printing as flat as possible, and for this purpose 
a plate of copper as useft for engraving is first procured. 
This is blackened with the sulphuret of potassium, in order 
that the draftsman may be enabled to judge of the effect 
which his drawing would produce, as he proceeds with his 
work. This blackened plate is warmed, and then coated 
with a compound of Burgundy pitch, white wax, rosin, 
spermaceti, and sulphate of lead, previously fused together. 
This composition, which is nearly white, must be uniformly 



322 GLYPHOGRAPHIC PROCESSES. 

spread over the plate, and the thickness should be about the 
one-thirtieth of an inch. The plate is now ready for the 
artist, who cuts through the white composition completely 
down to the blackened copper, and in fact with the ex- 
ception of that precaution makes his drawing in the usual 
manner. In the selection of tools the artist should be 
guided by the manner in which they can completely and 
clearly cut out the composition ; for it is important to make 
a clear indentation and not to turn aside the coating and 
leave a burr. A simple hook fixed in a wooden handle, a 
hook filed away on one side which most effectually cuts away 
the composition, or a piece of wood tapering to a fine point, 
are the forms particularly recommended by Palmer. The 
former instrument is best adapted for very fine lines, the 
second for larger lines, and the last for foliage and other free 
drawings and designs. 

When the artist has finished his drawing, the parts of the 
composition which are removed leave black lines, which 
have precisely the same relation to the white ground as the 
black lines in the subsequent print have to the white paper ; 
so that a most important feature in Palmer's operations, is 
the exact similarity between the design and the print. 

Many improvements have been made in the process since 
the former edition of this work was published ; such for in- 
stance, as giving a greater depth to the lights ; for the ground 
through which the drawing is made being necessarily very 
thin, printers found great difficulty in keeping their work 
clean. To alleviate this the plate is now submitted to the fol- 
lowing process. 

A roller being made of glue and treacle, such as is used by 
printers for inking their work, is charged with a composition 
of gum thus, turpentine, litharge, and read lead, and then 
passed lightly over the drawing, taking care that the roller 
is very lightly charged in the first instance, that it may not 
stop up the work. When this coat has become dry, which 



GLYPHOGRAPHIC PROCESSES. 323 

it will in a very short time if put on thin, the operation must 
be repeated again and again, until a considerable depth has 
been given to the work. 

The required depth having been obtained for the general 
work, broad lights should be built up by means of brushes 
with the same composition containing more litharge and 
sulphate of lead, or any other composition which will tend to 
aid the drying, and is not acted upon by the copper solution in 
the subsequent process. This part is very essential, or in print- 
ing the paper is pressed to the bottom of what is intended to 
be a light, and the effect destroyed. 

The operator must now allow the whole to get hard, 
and then with a magnifying glass go carefully over it, and 
remove anything which may have accidentally got into the 
lines. He must also then carefully brush it over with the best 
plumbago, taking great care to brush all out of the lines, or 
the block, after it is formed, prints rotten by the lines not being 
sound and firm. 

The drawing is now ready to receive a deposit of copper, 
and the power of the battery must be carefully regulated to 
prevent too rapid a deposition, or the copper is apt to grow 
over some parts if the line is not well cleaned out, and disap- 
point the artist by work not being copied, which he imagined 
he had put in. 

Having obtained a sufficient thickness in the electrotype 
trough, and this must vary according to the size of drawing, 
the deposited plate is separated, and the back trimmed to 
receive a layer of type metal, and then, having made the face 
perfectly flat, the back is turned off and mounted upon a 
block of wood similar to a stereotype. Many touches to 
relieve different parts may then be readily put in by a person 
accustomed to use the graver ; indeed much time is saved 
by removing the composition altogether in some parts, and 
putting in any little touches afterwards to give relief to the 
darks. 



324 GLYPHOGRAPHIC PROCESSES. 

This deepening of the work by the rolling process was a 
great improvement, by giving to the artist a plate with a 
much thinner ground than was at first used ; but it was 
subsequently found by Mr. Hawkins, who now carries on the 
process, that he could likewise form a block upon a common 
etching ground, which had been so much desired by those 
accustomed to etching; indeed practice has now enabled 
him to form a surface block from almost any engraved 
plate. 

Many very beautiful subjects have been done by this 
process. Some of the most successful are those well known 
prints of the "Bottle," by Cruikshank ; but the subjects 
best adapted, are maps, or writing of every description, and 
here it stands unrivalled both for price and quality. Messrs. 
Chapman and Hall, the publishers, are at this time bringing 
out a series of electro-glyphographic maps at one penny each. 
A series of very excellent copy-books have also been done 
by this art, and it has also been employed for bankers' 



Fig. 39. 



cheques. Messrs. Blackie and Son, of Glasgow, are now 
publishing a very valuable work entitled the Imperial Gazet- 
teer, the maps of which, executed by this process, appeared to 
me so excellent, that I wrote to those gentlemen, and they 
kindly lent me one of Bordeaux, which I am enabled to give as 
an example of the value of this kind of printing. 

Such are the principal features of Palmer's glyphography ; 
and although it did not answer the patentee's expectations by 
a speedy return for his labour and capital, it is now being very 
generally adopted for the purposes which have just been 
described. 




ELECTRO-TINT 



325 




Fig. 40. 

We have yet another branch of art to describe, which is an 
invention called the electro-tint, and which may be dismissed 
in a very few words. A plain copper-plate is procured, 
upon which the artist makes a painting with some substance 
insoluble in the solution of sulphate of copper. The plate is 
placed in the solution and a reverse made, which is at once 
ready for the printer. 

A great many specimens of the electro-tint have been 
published at different times, and of various degrees of ex- 
cellence, but the best that I have seen is a small portrait of 
Lance, by himself. There is something very pleasing in 
this print, and it shows at what perfection the art might 
eventually arrive. Sometimes the electro -tint cast is used to 
print from the hollows, at others from the elevations-: thus, 
in one case it forms a kind of engraving, at another a 



326 APPLICATIONS OF ELECTROTYPE. 

surface similar to that of a wood-cut. The first idea of the 
electro-tint was published in the Phil. Mag., June, 1840. 

(272.) The different cases in which electro-metallurgy is 
serviceable for the various departments of printing have 
been now described, and extensive as is their present 
application, doubtless still there is much to be effected in 
this department alone. It appears to me that the general 
name of electrotype ought to be restricted to these cases ; 
for although the propriety of the term when thus employed 
cannot be doubted, yet an extension of its use for dissimilar 
purposes is certainly inaccurate. The electrotype, therefore, 
I consider as one of the subordinate branches of the general 
science of electro-metallurgy ; though, doubtless, as the 
importance of the art of electrotyping for our manufactures 
is extremely great, so also its interest is increased from its 
being the first department in which the electric fluid has 
ever been used extensively to further the manufactures of 
the country. 






327 



CHAP. VI. 

ON MULTIPLICATION OF THE DAGUERREOTYPE. 

» 

Value of the Electro-Metallurgy for the daguerreotype, 2*73. Process 
for obtaining the duplicate, 274. 

(273.) Papers and periodicals from time to time have 
contained accounts of the multiplication, in copper, of these 
splendid works. The success, however, which at first at- 
tended these operations, I am afraid was not so great as has 
been reported. The image on the copper duplicate was 
sometimes moderately distinct ; but it did not become visible 
till it had been exposed to the sun's rays. Sometimes nothing 
was left on the original plate, nor was anything visible 
on either till exposed to the light. On the original, how- 
over, the image never returned ; but the plate was uninjured 
and therefore might be employed again. The copper de- 
posited upon a great number of plates had not the faintest 
trace of any view upon it. In some of these cases, the 
image was transferred from one plate to another rather than 
multiplied, because there was no increase of images, the 
image on the silver being only removed to the reduced 
copper, leaving the original plate quite plain and polished. 
In other original plates, however, a faint image was left. 
The Daguerreotype processes have been much improved of 
late years : the faint images first produced have given way to 
the most lively and distinct impressions. These impressions 
may very readily be multiplied, and the copper duplicate is 
in no way inferior to the original, although it requires to. 
be very carefully protected from the action of the air. -It 



328 PROCESS FOR MULTIPLICATION. 

appears to me that there is a good opportunity for a large 
business to be done in multiplied daguerreotype plates, as 
when once a good original was obtained any number of electro 
copies might be sold. 

Electro-metallurgy seems to be useful for the daguerreo- 
type in other ways besides the multiplication of the image, 
as sometimes a thin layer of gold is deposited, which fixes 
permanently the image, and gives it a peculiar tint. Per- 
haps it might be a good plan to platinize or iridize the 
plate, as the impression might then appear black and white. 

Some experimenters find that their silver plate is much 
improved by a very thin electro deposit of silver, as by that 
the plate is rendered more sensitive. 

(274.) The process for the multiplication of the daguerreo- 
type is similar in all respects to that detailed for the multi- 
plication of plain plates. The film of air so often noticed 
must not be forgotten for the daguerreotype. 

Mr. Home, of Newgate street, who is well known for his 
thorough knowledge of both the electrotype and daguerreo- 
type processes, in answer to my inquiries, has obligingly 
favoured me with the following account of the best modern 
process of multiplying daguerreotypes. That gentleman 
states that as soon as the plan of Monsieur Fezeau, of fixing 
the image with a weak solution of chloride of gold in hypo- 
sulphate of soda, became known, the daguerreotype pictures 
assumed a much higher importance. That which before 
could only just be seen then became a firm, bold picture, 
capable of being copied with ease. Great care, of course, is 
necessary to prevent the plate from being stained, and therefore 
the metal must be deposited as rapidly as possible, and we 
must by no means allow the plate to remain in solution 
without galvanic action. The solution must also be very 
bright and quite free from all foreign substances which can 
in any way attach themselves to the face. 

The single-cell, used in the following manner, will be 



PROCESS FOR MULTIPLICATION. 329 

found to answer best for commencing the deposition ; but as 
soon as the plate is well covered then it may be removed to 
an acid solution, and the deposit carried on by means of a 
battery. 

Take a saturated solution of sulphate of copper, and 
having filtered it, as before described, and placed a porous 
tube containing the proper acid and water in the same 
vessel, unite the daguerreotype at the corner to a zinc plate 
by means of a w T ire having a binding screw at each end. 
The wire must be long enough to allow both zinc and 
picture to go at the same moment into their respective 
solutions, by which means galvanic action is instantly set 
up, and a deposition immediately takes place over the whole 
of the surface, without allowing time for the* plate in any 
way to be acted on. 

Care must be taken not to remove the plate too soon 
from the solution, but any air bubbles are best removed by 
allowing a stream of water for an instant to flow over the 
surface. 

As soon as the required thickness has been obtained, the 
zinc plates must be separated, and the original daguerreotype 
plunged into clean water to remove all traces of copper, 
and finally dried off in the usual manner, whilst the de- 
posited copper should be protected as much as possible from 
the air. 

With respect to the above account, I am of opinion that 
the battery process may be safely used throughout, if ample 
power is supplied at first by using two batteries in series. 

It is necessary here to call the attention of my reader 
to the fact that, notwithstanding Monsieur Daguerre was 
liberally rewarded for his invention in his own country, 
and France proudly vaunted her liberality in giving his 
discovery to other nations, yet a patent is taken out in 
England, which renders it illegal to apply it for sale without 
the especial license of the patentee ! 

16 



330 



BOOK THE SIXTH. 

ON GALVANIC ETCHING. 

Action on the positive pole, 275. Etching by nitric acid, 276. Faults 
in the biting, 277. Galvanic etching, 278. Accelerating circum- 
stances, 279. Advantages of galvanic etching, 280. Gradations of 
tint, 281. General remarks, 282. 

(275.) All cur previous operations have been conducted at 
the negative pole of the battery; but at the positive pole 
certain effects take place which may be taken advantage of in 
the arts. Let us call to mind the fact, that gold, silver, and 
all metals with a greater affinity for oxygen, are dissolved 
when made the positive pole of a cell charged with a solution 
of the same metal. Now the relative distance which is main- 
tained between the positive and negative poles affects the 
degree of solution which takes place. This property may be 
easily shown by attaching a wire by one of its ends to the 
silver of the battery, and placing the other in a solution of 
sulphate of copper in the bottom of which a piece of copper 
connected with the zinc of the battery is immersed. After a 
short time the wire will begin visibly to be dissolved, and the 
part nearest the negative metal will be affected ; this will go 
on till the wire is dissolved, in such a manner that the part 
nearest the negative metal will diminish to the sharpest 
point, and the different amount of action will produce a per- 
fect taper. 

(276.) Although this property is of no value in its applica- 
tion, yet I have introduced it to show the facility with which 
the copper in every place is dissolved exactly in proportion 



ETCHING BY NITRIC ACID. 331 

to the electricity passing : and this is likely to be extremely 
valuable for engravers in their etchings. The term etching, 
is given to those engravings where the lines are not cut by 
any instrument, but are dissolved out by an acid. In order 
to make an etching, a copper plate is first to be prepared by 
covering it with a substance which protects it from the 
action of. the acid in which it has to be immersed. The 
substance used for this purpose is composed of asphalte and 
wax in equal proportions, combined with a fourth part of 
both black pitch and Burgundy pitch. This mixture is 
placed in a piece of silk, and rubbed over the copper plate 
which is kept at a moderate heat, by holding it over a lamp 
or chafing-dish. This operation is technically called laying 
a ground ; this at first is colourless, but it is afterwards 
blackened by holding it over the flame of a candle, and 
depressing it till a copious supply of smoke covers the 
surface. 

The engraver, with an instrument like a needle, called an 
etching point, executes his drawing, and in so doing removes 
the ground, and exposes a clean surface of metallic copper. 
The plate is then placed in a dish, and dilute nitric acid 
poured upon it, till the copper is dissolved out from the 
exposed lines to a sufficient depth. The plate is not allowed 
to remain in the acid a sufficient length of time to bite 
deeply, as this would cause the engraving to be of one degree 
of blackness ; but after it has been in the acid a short time, 
those parts which are required to be of a light shade are 
stopped out, that is, they are covered with Brunswick black, 
or a coat of varnish capable of resisting the action of the acid ; 
the plate is then replaced in the dilute acid, and after a time 
it is again removed, and a farther portion is stopped out ; and 
these operations are repeated as many times as there are dif- 
ferences of shade required in the engraving. The degree of 
perfection that the professed engraver obtains by practice is 
truly extraordinary, considering the uncertainty which must 



332 PROCESS OF GALVANIC ETCHING. 

attend the operation; for the action of nitric acid is not 
subject to any regular laws, and moreover is never alike over 
all parts of the same plate. This is owing to the copper 
plate itself being never pure; but always containing tin, 
dispersed here and there throughout its texture, which re- 
sists the action of the acid. After a splendid plate is bitten 
m, some portions are sometimes left which cannot be acted 
upon by the nitric acid, but absolutely require the graver to 
bring up the fine lines. 

(277.) No engraver that I have conversed with, can explain 
the cause of these faults in their work, but to the chemist they 
are perfectly intelligible ; the nitric acid attacks the copper, 
forming a soluble nitrate of that metal which is dissolved in 
the fluid ; but the action of nitric acid on tin is altogether 
different, for it converts the metal into a peroxyde, which 
being insoluble, protects the copper from the acid. The en- 
gravers have always noticed this white powder (the peroxyde 
of tm), so fatal to the success of their operations. 
. i 218 -) Etching by galvanism is a far more certain opera- 
tion than the foregoing, because it can be reduced to known 
principles. In this case, the plate to be bitten in has the 
device first drawn upon the same ground that is used in the 
ordinary process; the back and edges of the plate are then 
coated with wax, and it is to be connected, by means of a 
wire, with the silver plate of one or two of my batteries. 

The size of the negative pole of copper, I stated in my 
former edition, should be as large as the positive or etching 
plate ; but subsequent experiments have proved that to bite 
with greater regularity and sharpness, the relative size of 
the two plates should be as dissimilar as possible ; for that 
purpose, a fine wire should be preferred, and when an equal 
depth is required, should be equi-distant from every part of 
the plate. 

The piece of copper to form the negative pole should then 
be connected to the zinc, when both the copper-plate and 



ADVANTAGES OF GALVANIC ETCHING. 333 

the piece of copper are to be placed in solution of sulphate 
of copper. Immediately copper will be reduced from the 
solution on the the negative plate, and copper from the 
etching plate will be dissolved to keep up the strength of the 
solution. 

Whatever is favorable to the increase of electricity, 
causes the copper to be more quickly acted upon, and what- 
ever diminishes the galvanic current, retards the solution of 
the metal ; the nearer the etching plate forming the positive 
pole and the piece of copper forming the negative are ap- 
proximated, the more rapid will be the action. In the 
same way, the intensity of the battery also affects the 
rate at which the plate is bitten in. The negative i late of 
copper, however, should not exceed in size the copper-plate 
on which the etching is executed, or else there is a risk of 
some of the lines being more deeply bitten in; and, in like 
manner, if any considerable part of the plate has a great 
deficiency of lines compared with other parts, that part must 
be stopped out rather before the other, to insure a uniformity 
of depth, or else the negative copper opposite this part must 
be bent in such a way as to increase the distance. 

(279.) The advantages of galvanism for etching, are, the 
absence of poisonous nitrous fumes, which are evolved in 
the ordinary process ; the greater uniformity of action which 
takes place than when the acids are used ; and the rapidity of 
biting, which may be regulated to the greatest nicety ; the 
lines may be made of any depth, and are sharper and cleaner 
than when acid is used ; and lastly, no bubbles are evolved, 
which the engraver well knows are apt to tear up the ground, 
or to cause unequal action. 

The exact quantity of copper dissolved from the plate 
can be ascertained by weighing the metal reduced on the 
sheet of copper which forms the negative pole, or by mea- 
suring the quantity of hydrogen evolved from the silver 
plate of one of the platinized silver batteries ; for thirty-two 



334 ON EXECUTING GRADATIONS OF SHADE. 

grains of copper will be dissolved for every forty-eight cubic 
inches of gas evolved. 

Etching by galvanism can be executed with any desired 
degree of rapidity, according to the series of batteries to 
which the plate is connected ; but I believe that the practi- 
cal man will find that the action should neither be too slow 
nor too quick, and perhaps two or three batteries, arranged 
as a series, will be found best adapted, though a single cell 
would suffice. 

(280.) Galvanism would be valuable to the engraver for 
executing gradations of shade, such as, for instance, the 
effect of a strong light illuminating a whole room. The most 
simple manner in which this can be shown, is to take a 
copper plate and draw a number of lines on the ground with 
a ruling-machine. The plate, after having its back and 
edges coated with any non-conducting substance, should be 
then connected* with the silver of the battery, and copper 
wire. These two should be then arranged in the solution 
of sulphate of copper, that at one end they nearly touch, 
while at the other they are widely apart. By this position, 
the greatest quantity of electricity would pass at that part 
of the plate where it is nearly in contact with the negative 
pole, whilst the least would pass at the opposite extremity. 
The action on the etched plate being exactly in proportion 
to the quantity of electricity passing, is unequal over the 
whole length oi the plate, being greater where the metals 
are nearest, and gradually diminishing to the other end. 
This is the most perfect mode by which it is possible to 
obtain a gradation of shade. Many variations in the ar- 
rangements might be made by using, as a negative plate, 
a wire or a rod of copper, placed over the centre of a pre- 
pared plate ; for then a perfect gradation would be obtained, 
extending in all directions from the dark centre. In the 
. same way, two or more radiating shades may be obtained, 
by using two or more negative wires. An insensible gra- 



GALVANIC ETCHING. 



o 



35 



dation might be made from the darkest shade at the external 
edge of the plate, to the lightest point at its centre, by 
cutting out a hole in the negative piece of copper, opposite 
the part where the transition into light is required. 

The professed engraver who once practically masters 
the galvanic method of etching by the theoretical princi- 
ples which I have here detailed, is sure to obtain great 
results. He could easily execute the most extraordinary 
transition of light into darkness, with fidelity, and with the 
utmost certainty. However, I trust that the value of electric 
etching will not be confined to the artist ; for, by removing 
the disagreeable consequences attending the use of nitric 
acid in the present mode of etching, more persons may be 
induced to enter into it, and by this means, numbers 
studying the sciences will be enabled to execute an etching 
of those subjects which are curious and rare, to send to their 
brethren who are studying the same subject. Those travel- 
ling in foreign countries, or in picturesque situations, might 
transmit to their distant friends an idea of the sublimity and 
grandeur of the scenery which they are enjoying, or of the 
appearance of the towns and villages through which they 
are passing. In fact, there is not a person who might not 
be benefited by receiving etchings from others, and who 
might not, in return, circulate engravings of those objects 
which he may see. Pictorial representations are avowedly 
better than any verbal descriptions, so that there is ample 
scope for any one to exercise his talents usefully; and 
certainly many cannot be aware that etchings are not more 
difficult to execute than common pencil drawings. The 
process is as suitable for ladies to practise in their drawing- 
rooms, as are any of their usual amusements ; the operation 
being attended with as little trouble. It is necessary at first 
to have the plate prepared, or have a ground laid (which 
might be done by a workman), and at the conclusion of the 
drawing it has to be bitten in. The objection to this, 



336 MR. grove's process. 

hitherto, has been the disagreeable properties of the acid, as 
it is likely to spoil clothes or injure furniture ; but now that 
these objections are removed, I trust that numbers will enter 
into this amusing and useful branch of art. 

Mr. Grove has lately extended this process of galvanic 
etching, to the etching of daguerreotype plates. He ar- 
ranges the silver plate as the positive pole in a trough, by 
connecting it to the negative plate of a battery. He employs 
the silver plate about the same size as the daguerreotype ; 
but, I believe, he would find that he would be able to bite 
much deeper by following the improvements in galvanic 
etching described in a former part of this chapter. It is 
stated that these etchings, when printed, show extra- 
ordinary minuteness of detail. Up to the present time I have 
been unable myself to conduct experiments upon the matter ; 
but it appears to me that the process should be conducted 
upon the principle of the current taking the easiest road, to 
the exclusion of the rest. 



337 



BOOK THE SEVENTH. 

ON ELECTKO-DISRUPTIVE ETCHING. 

Process and practical application of the disruptive discharge to the 
, etching of steel, 281. 

(281.) It is well known that when the connecting wires of 
a battery are brought together, a spark ensues, and portions of 
that piece of metal communicating with the silver, are trans- 
ferred to that metal communicating with the zinc. To Dr. 
Pring is due the merit of having first brought this fact into 
practical use for the purpose of engraving the hardest steel. 
This gentleman fixes the plate to be engraved in a small hand- 
vice, such as is used by watchmakers ; this plate is then con- 
nected with an electro-magnetic coil, which is again connected 
with the zinc of about half a dozen of moderate-sized plati- 
nized silver batteries. To another wire, attached to the platinized 
silver, is joined a wire of platinum or of gold, which it is found 
convenient to fix in a crochet needle holder. When this wire 
is brought into contact with the steel plate a portion of the 
latter is thrown bodily off and transferred to the etching tool, 
and thus by electro-mechanical skill a perfect device can be 
made upon the hardest steel. 

If the plate and graver be attached to the reverse plates of the 
battery, then the wire is transferred and a gold or platinum 
design is effected ; but this result only takes place well in the 
purest steel, and the steel around the deposit is charred and 
burnt. 

Dr. Pring's process is at present a scientific curiosity of high 

16* 



338 ELECTRO-DISRUPTIVE ETCHING. 

interest ; it bears the same relation to the arts now as the first 
electro copies of penny pieces did many years ago ; in it is 
involved, however, a new application of a scientific fact, and on 
being thoroughly worked out may be, for aught we can tell, 
applicable to the die sinker and other branches of the arts, and 
is now applicable to imprint the most beautiful designs on 
swords and steel instruments of every description made of 
hardened steel, which would, by any other process, be difficult 
to engrave. 

The electro-disruptive etching is totally distinct from voltaic 
etching. In the latter, the voltaic force assists chemical affinity, 
and the metal is dissolved. In the former, the aggregation of 
the particles of metal is interfered with, and portions are thrown 
out. In the one case we act, therefore, by interfering with the 
attraction of chemical affinity ; in the latter, by interfering with 
the attraction of cohesion. This process was submitted to the 
Koyal Society in 1846, and with the peculiar wisdom for which 
that greatest association of philosophers in Europe are particu- 
larly notorious in their corporate character, it was allowed to 
slumber ; and from the circumstance of the inventor living in 
the country, it is even up to the present time but imperfectly 
known. The specimens which I have seen are extremely beau- 
tiful, and I hear that very interesting examples will be shown 
at the Great Exhibition. 



339 



BOOK THE EIGHTH. 

ON VOLTAIC BLASTING. 

On blasting rocks or sunken vessels under water, 282. Electrical 
' clocks, 283. Improper uses of electricity. 

(282) There are purposes besides electro-metallurgy for 
which the galvanic force is applicable to the wants of mankind, 
and of the most conspicuous of these is the mode of blasting 
by voltaic-electricity. This beautiful idea was first adopted 
by Mr. Martyn Roberts, who used it for blasting in mines; 
but for blasting under water was first put in practice by 
Maior-Gen. Pasley, who I believe was the first who adopted 
this system of blowing up sunken vessels. Whilst engaged 
in operations on the River Thames, he was written to by 
Mr Palmer, who recommended him to employ the galvanic 
battery instead of the long fuse then in use. After having 
been shown in what manner the voltaic battery was applic- 
able to his wants, he instantly adopted it and has since 
turned it to good account in the removal of the meek of the 
Royal George. He at first used Daniell's battery, but when 
I visited the lighter, he had abandoned the professors 
battery, and simply used an ordinary sulphuric acid battery. 
Captain Fisher, "the Harbour-Master of the River Thames, 
has used extensively this process for the removal of wrecks. 
This gentleman has also found voltaic blasting of great value 
in removing hard shoals of concrete, which continually form 
in the bed of the river, and which could not be removed by 
any other method. The nature of the proceedings which 
Captain Fisher adopted I am enabled to give with more 



340 



BLASTING BY VOLTAIC ELECTRICITY. 



minuteness, which will serve as a guide for others requiring 
similar proceedings. The barrel in which the powder is 
placed had a hole bored in it, so that it might admit a copper 
tube (t). This copper tube had a plate soldered to it at the 
upper part by which it might be fastened by copper nails to 

Fig. 41. 




the cask ; a plug (H) was fixed in the tube, through which 
two copper wires were inserted, and round the end of the 
wires was wound a fine piece of platinum wire (p), so that 
but a single filament extended from wire to wire ; the rest of 
the tube was filled with fine powder, and a piece of cork (c) 
was placed on the other end. This copper tube was then 
carefully secured water-tight by smearing pitch round the 
copper. For securing the tube and wires in .their place, the 
ends of the two copper wires were bent and nailed to the tub. 
The next thing was to fill the tub with blasting-powder by 
another hole, and then secure the aperture water-tight with 
a wooden plug, which was afterwards smeared over with 
pitch. The cask was then lowered to the bottom of the 
vessel, and placed in the situation where it was destined to 
act. A rope, previously made by procuring two wires first 
covered with cotton and varnished, and twisting them with 
the texture of which the rope is made, was then lowered to 



ADVANTAGES OF GALVANIC BLASTING. 

the bottom of the sea, and the ends of the two wires com- 
municating with the tube were tightly lashed to the two 
wires in the- rope. All the wires should be now insulated 
by gutta percha, as that material effects the object in the 
most perfect manner. All these things being ready, the 
ends of two wares at the other extremity of the rope were 
connected with the two extremities of a small compound 
platinized silver battery, when immediately on contact being 
made the explosion took place. 

The galvanic force is also now employed for telegraphic 
and other purposes, of which a description would here be 
given if it did not require a too great extension of the work. 
I have been compelled, however, to introduce the mode of 
blasting, from the frequent inquiries made about it, and the 
great benefit which the process affords to the operator, by 
diminishing materially the risk of accident to those engaged 
in mining operations. The great advantage of galvanic 
blasting is dependent on the source of heat not being applied 
till the moment it is wanted, and then being instantaneous ; 
whereas, in the former modes of proceeding, it frequently 
takes place after it is expected, when the workman impru- 
dently approaching to see the cause of the delay is in- 
stantaneously mutilated or destroyed. The employment of 
galvanic batteries in mines, ought to be peremptorily en- 
forced ; for but a few batteries would suffice for the largest 
mine, and as the immersion in the liquid need not be longer 
than half a minute for each explosion, the charge of acid 
would scarcely require to be changed once a month, and 
consequently but little destruction of zinc would ensue. 
The battery might be fixed to some secure situation, and the 
workman would then only have to move the rope to the spot 

desired. 

When Sir Harry Smith desired to astonish the natives of 
Africa, having previously arranged the contrivances required 
for voltaic blasting, he told them that, as an example of 



342 ELECTRICAL CLOCKS. 

power, he would show that he could * at any definite mo- 
ment command the waggon to go to pieces. The word of 
command was given, the circuit was completed, and, to the 
astonishment of the Africans, the whole was blown into 
the air. 

Electricity has been brought to bear to give the motion to 
clocks. Messrs. Shepherd, of Leadenhall Street, have con- 
structed electric clocks worked by four or five of my batteries, 
which have attracted much attention amongst the scientific. 
These ingenious mechanical inventors have constructed a 
very interesting electrical clock for the Crystal Palace, 
which, doubtless, will much interest foreigners. 

Besides the useful purposes of electricity, it might some- 
times be made to play the part of the marvellous ; and 
doubtless Wiseman, Faber, and such others, who seek to 
rule mankind by acting upon their credulity, rather than 
their reason, when they have caught a victim and safely 
concealed him in a religious house, away from his friends, 
might, in addition to their present modus operandi, manu- 
facture apparitions of good and evil spirits, the better to 
assist their ordinary mental processes. Electrical apparitions 
might produce marvellous effects, if used in a solitary 
chamber upon either a fatuous female, or a youth bewildered 
by theological dogmas ; but I feel sure that there is no elec- 
trician who would lend his aid for such a purpose, but would 
rather seek to destroy the heathenish darkness of priestcraft 
by the illumination afforded by the light of science. 



348 



CONCLUSION. 



I have now detailed briefly, but I trust usefully, the pro 
perties of bodies which are called galvanic, and the effects 
which galvanic batteries produce, as far as relates to the in- 
teresting subject of electro-metallurgy. Our science, even in 
itself, is essentially dependent upon galvanism, and the pre- 
cipitating apparatus employed is nothing but a battery cell. 
With regard to the laws regulating the metallic deposit and 
the metals capable of being deposited by the voltaic current, 
these are derived from my own observations. The importance 
of these laws to the operator, will be to enable him to proceed 
with certainty. The reason which has induced me to devote 
so much labour and thought to these laws, has arisen from a 
conviction that the electrotype must have been abandoned un- 
less the operator could proceed upon certain fixed principles. 
The extension of the few isolated facts formerly known, and 
their enlargement into a general science will, I trust, be found 
useful to those engaged in prosecuting these operations. 

The influence which this new branch of science will have 
on the arts, manufactures, and commerce of our great 
country, it is scarcely possible to foresee. The extended use 
of galvanism for manufactures requires the utmost encourage- 
ment, and the improvements must not be shackled by patents, 
if we desire the scheme to succeed ; for the ingenuity and the 
talent of the whole country is required to place it upon a 
firm footing. 

The multiplication of copper- plates will cause a far greater 
demand for them than has ever existed heretofore, and the 
engraver need be under no apprehension ; for not only will 



344 EFFECT OF THE ELECTROTYPE ON MANUFACTURES. 

W 

his talents be more required, "but he will be called upon to 
execute more splendid specimens of art ; for as these can be 
multiplied ad infinitum, a large circulation will render it 
worth while for any publisher to pay a very high price for 
an original which he conceives will meet with great public 
approbation. The publisher, in the same way, could lessen 
the price of engravings from our finest works of art, so as to 
bring them within the means of every person ; and there is 
no doubt that he who first engages in a business upon the 
above liberal and well known principles, will realise for 
himself a large fortune, and contribute greatly to the benefit 
of society. 

For our potteries, the multiplication of plates assumes a 
higher importance even than the last-described valuable ap- 
plications ; for it enables the manufacturer to improve the 
designs upon our otherwise perfect earthenware, and then 
all countries will indeed be jealous of what they are already 
otherwise inclined to look upon with envy. 

Our calico-printers will also now be enabled to use far 
more costly plates than they have hitherto employed. 

There are many other applications of this science besides 
those which I have already detailed ; such as the capability 
of adding copper to copper, and other similar purposes, 
which cannot be effected by any other process. Another 
important application of galvanism is, the means which it is 
likely to afford of separating one metal from another, or from 
its ore. 

A great variety of the applications of electro-metallurgy 
may appear to many to be trifling, as they contribute only to 
embellish the drawing-room and gratify the eye ; but let them 
remember, that as private persons engage in the manufacture 
of these little trifles, it leads to a knowledge, and a practical 
knowledge, too, of the effects of one of the most important 
and universal agents operating in nature. As manufacturers 
engage in it, it leads to a more general use of the galvanic 



ELECTRO-METALLURGY FOR BAD PURPOSES. 345 

battery, which, doubtless, will eventually hold an important 
place in our manufactures. 

It is true that electro-metallurgy offers many opportunities 
for fraudulent proceedings, as by it the forger can copy, with 
ease and unfailing accuracy, any embossed surfaces or stamps, 
and therefore no embossed work whatever should be used 
where there is likely to be any inducement for copying. By 
it seals may be forged, and an impression may be taken off a 
copper plate if it only remain in the possession of the party 
for a few seconds ; besides, our new science gives the false 
coiner many opportunities to further his fraudulent practices. 
These things are particularly pointed out to put people on 
their guard against the designs of bad men. 

Science, however, must not stop because some of its appli- 
cations are liable to be turned to bad account by the evil- 
designed ; and we must recollect that those things which can 
be forged by the electro-metallurgist, can also be forged by 
other processes before known. It was a favourite maxim of 
our great countryman, Wollaston, that, * whatever man can 
execute, man can also copy," and therefore the very idea of 
any device being inimitable is absurd. 

Of the value of electro-metallurgy to the arts and manu- 
factures, even in the present state of the science, there can 
be no doubt. It is not now a question of probability whether 
this science is practically applicable or not, for we have de- 
tailed what has been done by its agency ; we have given 
full descriptions of all the various processes for obtaining 
with certainty many results ; and finally, we have arranged 
all the facts into a tangible and systematic form, and, by 
laying down laws by which all its operations are govered, 
reduced the whole into a vast comprehensive science. 

It may be, indeed, a matter of conjecture, to what extent 
this science may be ultimately carried out, or to what other 
purposes it may be applied in years to come; but were it 
never to be applied otherwise than it has already been, — 



346 ELECTRO-METALLURGY DEPENDENT ON ELECTRICITY. 

were it to stop for ever at the point to which we have now 
brought it, — no one can deny that it is a most valuable acqui- 
sition ; in short, we may safely assert, that no other single 
discovery ever presented capabilities at once so many, so 
various, so interesting, or so valuable. 

This science depends for its very existence on electricity ; 
and among the indirect benefits which it may surely be 
hoped will arise from it, we may mention the study of elec- 
tricity generally, of which gigantic power so little is known, 
and which plays so important a part throughout nature ; for 
though all of us recognise its operation in the thunder-storm, 
and view with terror and amazement the devastating vio- 
lence with which, at such times, it makes known its power, 
yet, at present, how little do we know of the effects which 
it is at all times producing around us by its silent and con- 
tinued operation. 

The science of electricity is perhaps one of the most sub- 
lime examples of the might of human intellect, for by its 
agency man has made obedient to his will a power capable 
of producing such vast and terrible effects. " Nil mortalibus 
arduum est" says Horace, when speaking of Prometheus, 
who was fabled to have stolen fire from heaven ; and modern 
science has proved again and again the truth of this asser- 
tion, though little could he have thought, when writing the 
passage, how nearly the fable of Prometheus would in after 
ages become verified. 

To the young chemist, we would particularly recommend 
the study of this science, and should he be tempted to turn 
his attention to it in a systematic manner, he will be amply 
rewarded for his trouble. The results of his experiments 
are lasting, and will be contemplated by him in after years 
with pleasure ; whereas chemistry, being too often used as 
a source of amusement, brings forth very different results. 
The experiments tend to nothing, and end in nothing, 
beyond the present gratification ; they illustrate facts which 



SYSTEMATIC PROCEEDINGS NECESSARY. 347 



• 



have been illustrated exactly in the same way a thousand times 
before, and are usually selected to be gone over and over again, 
purely because they possess some incidental character which is 
calculated greatly to astonish the uninitiated spectator, though 
not to enhance the scientific acquirements of the operator. By 
such a course of proceeding (for undoubtedly such it very com- 
monly js) nothing is done, either directly by the operation, or 
by increasing the knowledge of the operator, and there remains 
nothing to show for the labour and money expended, except, 
perhaps, the trouble of clearing away the remains, or, what is 
not so easily accomplished, the rectifying of the mischief done 
to furniture generally. We have no hesitation in saying, that 
electro-metallurgy will afford as much or more gratification as 
an intelllectual pursuit, and infinitely greater satisfaction in its 
results. 

In conclusion, we cannot too often impress upon our readers the 
advantage of making themselves thoroughly conversant with the 
principles upon which the operations of electro-metallurgy de- 
pend, and the laws by which these operations are in all cases 
governed. By hurrying at once into the performance of the va- 
rious processes without thus qualifying themselves, what can be 
expected but failure and its consequences, — disappointment and 
mortification ? Proceeding in ignorance of the rationale of the 
process, untoward circumstances are for ever marring the designs 
of the operator ; experiment follows experiment, and failure 
follows failure ; materials are expended in vain, and, after the 
loss of much time, the student (if such he can be called) becomes 
tired of a science which has yielded him so little satisfaction, 
and throws it aside in disgust, perhaps attributing its uncertainty 
to that which is the pure and absolute result of his own idle- 
ness, and consequent ignorance. But if the student proceed in 
an orderly and philosophic manner, making himself first ac- 
quainted with the nature and modus operandi of the materials 
with which he is about to work, he cannot by any possibility 
fail in his results. With such preparation no casualty can occur 



348 PROSPECTIVE ADVANTAGES. 

•which cannot be readily referred to its true source, and conse- 
quently as readily remedied. Those who are comparatively 
unacquainted with electricity and galvanic apparatus may meet 
with some little trouble in entering upon the science of electro- 
metallury ; but commencing upon a right method, their first 
trouble will be their last ; and let them always bear in mind, 
that without trouble no great good was ever accomplished. 

Doubtless the galvanic fluid will, before long, be as important 
to the manufacturer as the heat of a furnace. At present a 
person may enter a room by a door having finger-plates of the 
most costly device made by the agency of the electric fluid ; 
the walls of the room may be covered with engravings, printed 
from plates originally etched by galvanism, and multiplied by 
the same force ; the chimney-piece may be covered with orna- 
ments made in a similar manner. At dinner the plates may 
have devices given by electrotype engravings, the salt spoons 
gilt by the galvanic fluid, and his table covered by costly electro- 
silver-plated ornaments. All these, and many other applica- 
tions, we may have at present, — but we must still look forward 
to the most important properties of the electric current derived 
from the galvanic battery ; for although great and glorious are 
the triumphs of science detailed in this work, yet the prospect 
of obtaining a power which shall supersede steam, exceeds in 
value all these applications. For to cross the seas, to traverse 
the roads, and to work machinery by galvanism, or rather 
electro-magnetism, will certainly, if executed, be the most noble 
achievement ever performed by man. 



APPENDIX, 



ON ELECTRO-METALLURGICAL PATENTS. 

The statute of Monopolies, (21 J. 1, c. 3), declares the confer- 
ring on any person the exclusive privilege of carrying on a 
particular trade, or manufacture, to be altogether contrary to 
the laws of this realm, and a species of offence, called mono- 
poly. The statute, however, excepts Letters Patent for the 
term of fourteen years and under, for the working or mak- 
ing of any manner of new manufactures within this realm, 
which others at the time of making such Letters Patent shall 
not use. 

A new manufacture may be the production of a new 
article for the first time, or a new mode of producing the 
same article either by an addition or omission of any part of 
the process, or, with regard to chemical patents, of some 
new specific process. A new manufacture may also consist 
of a new application and adaptation of some known agent or 
thing. 

It is essential that any of the above manufactures or pro- 
cesses should be a new invention " as to the public use and 
exercise thereof;" in other words, no patent is valid that is 
taken out for an invention in public use, although the practice 
in secret of any process, by a manufacturer, will not prevent 
another manufacturer from taking out a patent for the same 
process and forbidding the first. The prior publication of a 
process in a printed book in this country, under certain circum- 
stances, will vitiate a patent, though a process well known and 
freely practised abroad may be patented in this country. The 
new manufacture, in* any case, must be useful to entitle it to a 
patent; therefore, the slightest novelty attended with great 
good will justify a patent. 

For the inventor to secure to himself the exclusive right 



S50 APPENDIX. 

of a new manufacture it is essential that he should disclose 
his process in such a way that persons may use the same 
at the expiration of his patent ; and the spirit of the Eng- 
lish law seems to suppress monopoly, but to allow advan- 
tages for a limited period, to those who benefit their coun- 
try by adding or introducing any new and useful manufac- 
tures. 

The principle which guided our forefathers upon patents 
deserves the highest commendation, though the practice of 
their successors upon this subject cannot well be worse ; for, 
as now constituted, Letters Patent cause great expense to in- 
ventors who really deserve them, great injury and trouble to 
manufacturers from their being frequently granted where not 
deserved, and endless expense and litigation from their in- 
security when obtained. If the principle of patents according 
to the English constitution were strictly adhered to in prac- 
tice, nothing could more tend to improve and enlarge our mi 
nufactures. 

By reducing the expense of the patent, affording greater 
facility for procuring it when deserved, preventing the pos- 
sibility of its being granted improperly, and rendering it, 
when obtained, an absolute protection, the inventors would 
be directly benefited, the manufacturers protected, and the 
prosperity of the whole country would be enhanced by the 
monopoly, in the manner that the wisdom of our forefathers 
contemplated. 

From the preceding observations, the Electro-Metallurgist 
will perceive that it is not only essential that a patentee 
should have a patent to secure the monopoly of any manu- 
facture, but that he should have acquired it properly. For 
this reason it is by no means certain that the following 
patents are rightfully possessed, and therefore it would be 
wise in a person interested in any process to examine care- 
fully how far any patent interfering with his business is valid. 
The following list I have principally compiled from the 
" Repertory of Patent Inventions " and " Newton's London 
Journal," — particularly valuable sources of reference for these 
matters; and in these journals tolerably full extracts of 
a great number of electro-metallurgical patents have been 
given. 

There is a curious point of law connected with some of 



APPENDIX. 351 

these patents, and that is, particular processes have come 
into public use between the granting of a patent and its 
specification; and which process could not even be inferred 
in the slightest degree from the title of the patent. In these 
cases, common sense, doubtless, says that the patent ought 
not to prohibit the manufacture in common use; but what 
the law says lawyers alone can decide. Persons requiring in- 
formation on this subject may consult a chapter dedicated to 
these matters in Stephen's Commentaries on the Laws of 
England, book ii. part ii. chap. 3, or a very interesting little 
treatise by Webster, " On the Subject-matter of Letters Pa- 
tent by Invention," the author being a great authority on these 

points. 

If a true and valid patent is infringed, the inventor has 
his remedy by an action of trespass for injury sustained, and 
he may also obtain an injunction to restrain the continu- 
ation of the manufacture, and can compel the aggressor to 
deliver an account of the profit he has derived from the sale 
of the article. Moreover, any person using the name or 
mark of the patentee is subject to a penalty of 50/. The 
action may be resisted by showing that the patent is void in 
the manner already pointed out, or the patent may be for- 
mally impeached (if improperly obtained) in the Queen's name 
by the Attorney-General, or even by any other person with his 

consent. 

The first strictly electro-metallurgical patent was granted to 
James Shore, of Birmingham, merchant, for improvements m 
preserving and covering certain metals and alloys of metals. 
Sealed March 3, 1840. Enrolled in the Enrolment Office, 
Sept. 1840. The patentee claims the coating ot manufactured 
articles of wrought or cast iron, lead and copper, and its al- 
loys, with copper or nickel; such coating being effected by 
galvanic-electricity. ' „ . 

The next patent was granted to George K. Elkmgton and 
Henry Elkington, of Birmingham, for improvements m coating, 
covering, or plating, certain metals. Sealed March 25, 1840. 
Enrolled in the Enrolment Office, Sept. 1840. The patent is 
for the numerous processes of gilding, plating, <fcc, &c. 

The next patent was granted to Thomas Spencer, of Liver- 
pool, carver and gilder, and John Wilson of the same place, 
lecturer on chemistry, for certain improvements in the process 



§52 APPENDIX. 

of engraving on metals by means of voltaic-electricity. Seal- 
ed Oct. 7, 1840. Enrolled in the Petty Bag Office, April, 
1841. 

A patent was granted to Joseph Lockett, of Manchester, in 
the connty of Lancaster, for certain improvements in manufac- 
turing, preparing, and engraving cylinders, rollers, and other 
surfaces for printing and embossing calicoes or other fabrics. 
Sealed August 27, 1840. Enrolled in the Petty Bag Office, 
February, 1841. This appears to be an important patent con- 
nected with the cotton printing manufactures. 

A patent was granted to Willam Tudor Mabley, of Welling- 
ton Street North in the parish of St. Paul, Covent-gaden, in 
the county of Middlesex, mechanical draftsman, for certain im- 
provements in producing surfaces to be used for printing, em- 
bossing, or impressing. Sealed Dec. 17, 1840. Enrolled in 
the Rolls' Chapel Office, 1841. This patent seems to contain 
numerous applications of electro-metallurgy to printing sur- 
faces, but to what perfection he carries out his processes I am 
unable to state. 

A patent was granted to Alexander Jones, engineer, for im- 
provements in the manufacture of copper tanks and vessels. 
Sealed June 14, 1841. Enrolled in the Enrolment Office, May, 
1841. 

To George R. Elkington and H. Elkington, of Birmingham, 
for improvements in coating, covering, or plating certain me- 
tals. Sealed June 22, 1841. 

To Edward Palmer, of Newgate Street, gentleman, for im- 
provements in producing printing-surfaces, and in the printing 
of china, pottery, vases, music, and maps. Sealed June 12, 
1841. This patent is briefly noticed under the head Electro- 
tint in the text, and a little work dedicated to this subject has 
been written by Sampson. 

Specification of the patent granted to Islam Baggs, of Chel- 
tenham, gentleman, for improvements in printing. Sealed 
Jan. 23, 1841 ; enrolled 23rd, 1841. This is a very ingenious 
patent, whereby colours are given by means of the galvanic 
battery. 

To Ogilthorpe Barratt, of Birmingham, metal gilder, for cer- 
tain improvements in the precipitation or deposition of metals. 
Sealed Sept. 8, 1841. 

To W. IL Fox Talbot, of Laycock Abbey, Wilts, Esq., for 



appe^di::. 353 

improvements iii coating or covering metals with oth«r 
metals, and in colouring metallic surfaces. Sealed Dec. 9, 
1841. 

To Edward Palmer, of Newgate Street, philosophical in* 
strument maker, for improvements in producing printing, and 
embossing surfaces. Sealed Jan. 15, 1842. This important 
patent has been described under " Glyphography" in the 
text, and an illustration is given. 

To H. B. Leeson, of Greenwich, Doctor of Medicine, for 
improvements in the arts of depositing and manufacturing 
articles by electro-galvanic agency, and in the apparatus 
connected" therewith. Sealed June 1, 1842. 

To Edmund Tuck, of the Haymarket, silversmith, ft* im- 
provement in the covering or" plating with silver various 
metals and metallic alloys Sealed June 4, 1842. 

To J. S. Woolrich, of Birmingham, chemist, for improve- 
ments in coating with metal the surface of articles formed of 
nickel, or metallic alloys. Sealed August 1, 1842. 

To Alexander Parke's, of Birmingham, for certain improve- 
ments in the production of works of art in metal by electric 
deposition. March 29, 1841. 

To Alexander Parkes, of Birmingham, artist, for improve- 
ments in the manufacture of certain alloys or combination 
of metals, and in depositing certain metals, October 30$ 

1844. . 4 . 

To James Napier, of Hoxton, for improvements in treat- 
ing mineral waters to obtain products therefrom, and for 
separating metals from other matters, October 22, 1834. 

To Arthur Wall, of Poplar, for certain improvements in 
the manufacture of steel, copper, and other metals, December 

18, 1844. Tx ; tf i » 

To Louis Hypolite Piaget and Philip Henry duBois oi 
Wynyatt Street, Clerkenwell, Middlesex, November U> 

To' Thomas Lyon and William Millward, of the county of 
Warwick, for certain improved alloys of metals and im- 
provements in the deposition of metals, March 23, 1847. 

To Cyprien Maire Tessie du Motay, of Par*, for im- 

Movements in inlaying and coating metals with various 
substances, November 4. 1847. 



I 



354 APPENDfc 

To Sidney Edwards Nurse, of Ampton Place, Graves Inn 
Road, for improvements in the manufacture of plates or 
surfaces for printing and embossing. Sealed in Scotland, 
July 10, 1848. 

To Alexander Parkes, of Harborne, in the county of 
Stafford, chemist, for improvements in the deposition ane| 
manufacture of certain metals and alloys of metals, and 
improved modes of treating and working certain metals and 
alloys of metals, and in the application of the same to 
various useful purposes. 

To Thomas Henry Russell, of Wednesbury, and John Ste- 
phen Woolrich, of Birmingham, for improvement in coat- 
ing iron and certain other metals and alloys of metals. 
Sealed March 19, 1849. 

To Stanhope Baynes Smith, of Birmingham, in the county 
of Warwick, electro-plater and gilder, for improvements ttt 
depositing metals. Sealed June 7, 1849. 

Such is the list of those electro-metallurgic patents which 
I have succeeded in finding, but there may be many mor< 
which have escaped my diligent search ; and, besides these, 
we must remember that there are innumerable paragraphs 
slipped into other patents which refer to electro-metallurgu 
processes. When some men take out a patent, they contrive 
to slip in as much as they can find of other processes, so 
that the most opposite things are sometimes contained in the 
same patent. At the present time the whole practice of th< 
patent law is exceedingly bad. It neither rewards in- 
ventors nor benefits the public, but it appears that with 
this, as with other matters, it is easier to perceive th< 
defects^ than to point out a satisfactory remedy. 



ANALYTICAL INDEX. 



Absorption, by plaster of Paris, pre- 
vented, 135, 136. 
Acetate of silver, reduction of silver from, 
188. 
of copper, reduction of copper 
from. 201. 
„ of nickel, reduction of nickel 
from, 193. 
Acid solution of galvanic batteries, its use, 
8,10. 
„ of Darnell's battery, 19. 

„ of Grove's battery, 22. 

., of Smee's battery, 26. 

Action', local, 6. 

Adhesion of hydrogen to plates of Dattery, 
16, 17. 
„ of original and duplicate plates 

in electro-metallurgy, 109. 
„ cause of, 109. 
„ obtained or avoided, 109, 110. 
„ of air to metals, 110. 

of air bubbles to the moulds, 111. 
Air, film of, on metals, 18. 109. 
Air-bubbles, reduction of metals on, 111. 
Alkalies, compounds of, with oxides, 168. 
Alloys used for making moulds, &.c. 122. 
„ table of, 123. 

„ reduction of, 224. .•• 

Amalgamation of positive metal in batte- 
S ries, 16, 17. 195. 

gilding by, 237 
Ammonia, chemical equivalent, 49. 
Ammonio-nitrate, chloride, and carbonate 
of silver, reduction of silver from, 188, 
189 
Anaglyptograph, Bate's, 272. 
Animal electricity, 81. 
Anions, table of, 52. 

Anode synonymous with zincode, fcc. 44. 
Antimony, reduction of, 218. . 
Apparatus, single cell, for precipitation of 
metals, 87. 97. 
„ capillary tube, 93. 
„ plaster, 93. 

battery, 104. a . , _ 

union of battery and single cell, 

103, 104. 
Mason's, 105. 

Marsh's, for detecting arsenic, 
220. 
„ for reduction of gold, 184. 

Applegarth's machine, 318. 

tnastatic printing, 291. M . 

rsenic, detection of, by Morton's plan, 

by Marsh's appa- 
■ ■ ratus, 220, 



tt 


tt 


tt 


tt 


M 


» 


tt 


tt 


» 


tt 


It 


tt 


tt 


tt 


tt 


tt 


tt 


tt 



Arsenic, detection of, by galvanic precipi- 
tation, 222. 
Astatic needles, 39. 

„ galvanometer, 39. 
Atomic theory, 48. 

Aurocyanide of potassium, formation of, 
183. 
„ „ reduction of gold 

from, 145, 146. 
183, 184. 

Bate's anaglyptograph, 272. 
Battery, galvanic, discovery of, 2. 
„ „ requisites for, 3. 

H „ acid solution, 3. 8. 10. 

tf „ electro-negative plate, 4. 

ft n electro-positive plate, 4. 

„ local action in, 6. 
„ appearance in action, 6. 
chemical theory of 1. 
contact theory, 7. 
quantity, 9, 
intensity, 10. 
amount of action in, 10. 
power of, 11. 
compound, 13. 
various forms : — 
Couronne des tasses, 

13. 

De Luc's column, 13. 
" Hare's, 13. 

Cruickshank's, 14. 
other old forms, 13, 
" 14. 

Darnell's, 19. 21. 
" , Grove's, 22. 

Leeson's, 23. 
' Smee's, 24. 

, odds and ends', 28. 

n its properties :_ 

heating wires, 35. 
igniting charcoal 

points, 36. 
„ giving a spark, 36. 

charging Leyden jar, 
37. 
% M shock. 37. 

" magnetic effects, 38. 

" 41. 

• decomposition, effects, 

41, 42. 
Battery apparatus for reduction ot metals, 

9 7 > 98 - . * i ^ 
for reduction of plati- 
num, 176. 
for multiplying cop- 
per-plateS, 29^ 298. 



356 



ANALYTICAL INDEX 



Baskets, electro-coppered, 249. 
Baxter's process, 319. 

Bees'- wax and rosin for making moulds, 
131. 
„ „ for preparing plaster 

casts, 137. 
Bicyanide of mercury, 175. 
Bismuth, reduction of, from nitrate, 219. 

„ „ from tris-nitrate, 

219. 
„ „ from iodide, 219. 

„ „ from potassio-tar- 

trate, 219. 
Bisulphuret of carbon, 242. 
Black-lead, used for coating non-metallic 
substances, 144. 
„ first applied by Mr. Murray, 

xxii. 
„ application of, 144. 

„ test of quality, 145. 

„ for bronzing copper, 206. 

Black powder of platinum for Smee's bat- 
• teries, 24, 25. 
,, of metals, reduction of, 151. 

Bladder for porous tubes in Daniell's bat- 
teries, 19. 
„ for single-cell apparatus, 87. 
Blasting, galvanic, 339. 
Books to be consulted by electro-metal- 
lurgists, xxix. 
Brasses, monumental, multiplication of, 
274. 
„ mode of copying or " rubbing," 
275. 
Bread moulds, 143. 
Britannia Bridge, model of, 282. 
Bromide of gold, 181. 
Bronzing of copper by iron, 206. 

„ „ by black lead, 206. 

„ „ De la Rue's, 208. 

„ „ by grease, 206. 

„ „ by solution of plati- 

num, 207. 
., „ by sulphuret of potas- 

sium, 208. 
,, of clichees, 207. 

Brugnatelli first invents electro-gilding, 

XXV. 

Burnishing gold, 236. 
Busts made by electro-metallurgy, 282. 
Buttoning down of duplicate and original 
plates, 109. 

„ cause of, 109. 

„ avoided, 109. 

Cadmium, reduction of, from sulphate, 212. 
„ ., from chloride, 

212. 
n „ from ammonio- 

sulphate, 212. 
„ „ expense of, 213. 

Calico printing, process of, 304. 

„ application of electro- 

metallurgv to, 305. 
Capillary tube, apparatus for%eduction of 

metals, 93. 
Carbon, a conductor, 4. 

„ receives the metallic deposit, 121. 
„ for coating non-conducting sub- 
stances, 144. 
Casts, modes of obtaining, &i&. (See 
Mould.) 



Cathions, 52. 
Cathodes, 44. 
Cell of battery, 11, 12. 
„ single, apparatus, for reduction of 
metals, 87. 91. 
Chantrev, Sir Francis, his mode of making 

moulds from leaves, &c, 277. 
Charcoal points, ignition of, by battery, 36. 
., used for coating non-conductors, 
144. 
Chemical theory of the pile, 7. 
„ circular, action, 63. 
„ equivalents, theory, and table of, 

48. 
„ electro, decomposition, 51. 56, 
Chemico-mechanical battery, (See Smee's 

battery.) 
Chloride of platinum, 177, 178. 
„ of gold, 180. 
„ of iridium, 186. 
„ of cobalt, 223. 
„ of zinc, 208. 
„ of cadmium, 212. 
„ of nickel, 193. 
Chlorine chemical equivalent, 49. 
Chromes, metallic, 217. 
Clichees, process of making, 123. 125. 
„ from wood, 124. 
„ from plaster of Paris, 124. 
„ Italian mode of making, 125. 
„ by the press, 125. 
„ bronzing of, 207. 
,. from woodcuts, 215. 
Clocks, electric. 342. 

Coating, metallic, for non-conductors, 144. 
Cobalt, reduction of, from chloride. 223. 
„ „ from cobalto-cya- 

nuret of potassium, 
223. 
„ arsenite of, used in the potteries, 
303. 
Coiners, practices of, 121. 
Coining at the Mint, 263. 
Coins, list of, for electro-metallurgists, 
266. 
„ moulds from, 255, 
„ multiplication of, 255. 260 
,, old mode of making, 261. 263. 
Column, De Luc's, 13. 
Combustion of metals by the battery, 35. 
Composition for making wooden vessels 

water-tight, 101. 
Compouna battery, 13. 

., precipitating trough, 99. 

Conductors of electricity, 4. 
Conducting power of water increased, 4. 
„ „ of solutions vary with 

temperature, 57. 
„ substances capable of receiv- 

ing metallic deposit, 118, 
119. 
Constancy, meaning of the term, 21. 
„ of DanielFs battery, 20. 

„ practical, of Smee's battery, 

xxv. 
Contact, theory of the pile, 7. 
Copper, reduction of: 

,. from sulphate of, 194. 

196. 
„ from nitrate, 199. 

„ from muriate, 200. 

„ from acetate, 201 






ANALYTICAL IWDEX. 



857 



Copper, reduction of: 

vv ' from its compounds 

with ammonia, 201. 
from its oxyde, 201. 
from its iodide, 162. 
" 201. 

from its 6ulpho-cya- 

nide, 202. 
from cupro-cyanuret 

of potassium, 202. 
from its citrate. 202. 
from its tartrate, 202. 
from the double salts, 
" 203. 

in flexible state, 196, 

197. 
in greater crystalline 

state, 197. 
in state of extreme 
" brittleness, 193. 

in black powder, 198. 
time required for, 

103. 
positive pole of de- 
composition cell, 
203. 
negative poles, 204. 
by single-eell pro- 
cess, 205. 
by batterv apparatus, 

20.5. 
summary of various 

modes, 203. 
expense of, 115. 
reduced metal assumes the form 

of negative pole, 204. 
sheathing of vessels preserved, 5. 
positive metal of Daniell's bat- 

terv, 20. 
chemical equivalent, 49. 
used for receiving metallic de- 
posit, 122. 
„ bronzing of, 206. 
„ reduces copper, 61. 

electro-medallions of. 25b. 
multiplication of articles in, £&. 
plates for engravers, 292. 

present preparation ot. £3*. 
»..».•-* F value of these, 

" " 292. 

disadvantages 
" " of. 292. 

prepared by electrotype, 260. 
" 293. 

form of batten-, adapted, 
294. 
plates, form of precipitating- 
" F trough, 294. 

solution, best adapted, 29o. 
different qualities of metal, 
" 295. 

engraved plates. (See En- 

sTaved electrotpye.) 
medals. (See Medallions.) 
Coppering electro-medallions 258. 
fruit, leaves, &c, 247, /13. 

Srocess, 247. 
askets. 249. 
shins, 250. 

electro earthenware, 250. 
Couronne deg wssw. 13 



Crosse, Mr., on the galvanic spark, 36. 
Cruickshank's batten, 14. 
Crystalline deposit of metals, 148, 149. 

obtained with given so- 
lution, battery or ne- 
gative plate, 158. 
Current, voltaic. (See Voltaic.) 

„ measure of. (See \ oltameter 
and Galvanometer.) * 

Cyanide of potassium, formation of, 172, 

*173 
Cyanuret of potassium, formation of, 173. 

Daguerreotype plates, multiplication of, 
323. 
patented in this coun- 

trv, 329. 
etched by galvanism, 
336. 
Daniell's observations on copper reduced 
in his battery, xvii. 
view pf the decomposition of 

metallic salts, 55, 56. 
batterv : 
„ construction of, 19. 

attempts to improve, 20. 
constant effects of, 20. 
most constant form of, 
" 20. 

disadvantages of, 21. 
advantages of, 21. 
" removal of hydrogen, 21. 

Decomposition a property of the battery, 

laws' of, 49, 50. 
Faradav on the laws of, 49. 
electrolyticah. 51. 
electro-chemical or se~ 

condarv, 53, 54. 
of metallic salts, Professor 

Daniell on, 55, 56. 
effects of, only manifested 

at the poles, 56. 
affected by temperature or 

solution, 57. 
apparatus, 41. 
Decomposition apparatus, various forms, 

V-shaped tube, 

42. 
Faraday's vol- 
" " tameter, 42. 

new form, 43. 
" poles of, 44. 

" horizontal, com- 
" pared with 

vertical, 107. 
Definition of voltaic force, 62. 
Deflection of permanent magnet from vol 
taic current, 33. nnv , or r p. 

De la Rue's observations on copperre- 
duced in Darnell's battery, 
xviii. 
bronze, 208. 

BSnti*' v^/'electro-metaUurgy to. 

Dichromate of potash in Leesotf 6 battery, 

23 
Dies for coins and medals, 261. j»3. 
from embossed surfaces, tin. 



n 



?m 



ANALYTICAL INDK*. 



Die9 from paper, 276. 

Dig of the magnetic needle neutralised, 

Earthenware, porous tubes, 19. (See 

Porous.) 
«i *_• " ~ . P re cipitating troughs, 100. 
Elective affinity of original plate for solu- 
tion, 118. 
Electricity, various forms of, 2. 

„ voltaic, 2. 
Electric clocks, Shepherd's, 342. 

„ light, 37. 
Electro-disruptive etching, 337. 
Electro-magnetic machine, 82. 
l__ i. telegraph, 84. 

Electro, Barton's battery, 280. 
Electro-chemical decompositions, 53, 54. 
Electrodes, name given to the poles bv 
Faraday, 44 ""..""" * 

Electro-glyphography, 321. 
Electrolysis, 51. 
Electrolytes, 52. 
Electrometers, Harris's, 35. 
Electro, negative. (See Negative.) 
„ positive. (See Positive.) 
„ coppering, 245. (See Coppering.) 
„ gilding, 229. (See Gilding ) 
„ ironing, 252. 
„ leading, 251. 
„ nickeling, 240. 
„ platinating, 238. 
„ platinizing, 239. 
„ palladiating, 241. 
„ plating, 242. 
M tinning, 251. 
„ zincing, 251. 
„ magnetic apparatus, 82. 
m » shock, 82. 

„ medallions, 256. 
„ metallurgy requires a knowledge 

of galvanism, 343. 
r> n apparatus, 87. 168. 

» »> expense of, by various 

batteries, 112, 115. 
» »> applied to multiplying 

v, * „ medals, 253. 

Electro-metallurgy applied to multiplying 
seals, 269. 
« » n to multiplying 



•M 



brasses, 274. 
,, to multiplying 

emboss' d sur- 
faces, 276. 
»♦ to coppering 

fruit, &c, 277. 
» to sculpture, 

279. 
manufacture of silver 

articles by, 285. 
manufacture of copper 

articles by, 284. 
various other applica- 
tions of, 287. 
etching by. (See Etch- 

its effect on engrav- 
ings, 343. s 

prospective advan- 
tages of, 348. 



Electro models, 282. 
Electrotype, origin of, xvJt. 

„ Daniell's observations on the 

xvii. 

» De la Rue's observations, 

xviii. 

m Jacobi's idea of its applica- 

tion, xviii. 

ii Spencer's idea of its applica- 

tion, xviii. 

„ multiplication of type, 289. 

M multiplication of plain copper- 

plates, 293, 294. 

„ form of battery for, 294. 

H economy in, 297, 298. 

„ expense of, 299. 

„ multiplication of engrav 

copper plates, 300. 
multiplication of copper 
plates for the potteries, 304, 
and for the calico-printers, 
304. 

n multiplication of steel plates 

m copper, 310. 
h multiplication of wood-cuts, 

Electro-tint, Palmer's patent, 325. 
Elkington's water-gilding, 236. 
Embossed surfaces, multiplication of, 276 
Engraved copper plates, multiplication of 
300. 
»» »» relievos in cop- 

per, 300. 
» h relievos in lead, 

300. 
» m relievos in white 

wax, 301. 
>» >» relievos in plaster 

of Paris, 301. 
" » relievos in gutta 

percha, 301. 
» n formation of re- 

verse, 301. 
" tt back of reduced 

plate, 302. 
the "curd," 302. 
multiplication of, 
in copper, 310. 
» n multiplication of, 

in relievo, 310. 
Vnrrmn •" • " , . in silver, 311. 

Engraving, various kinds of, 302. 

., uses and applications of, 303. 

h line, 302. 

,„ mezzotinto, 303. 

Equivalents, chemical theorv of 48 49 
„ table of. 48. ' ' 

„ voltaic, 49, 

., of galvanic power, 48, 49 

_,,,.» expense of, 112. 114. 

Etching, preparation of plate, or lavin* 
the ground for, 331. 8 

execution of the design, 331. 
"biting; in." 331. & ' 

" stopping out," 331. 
uncertainty in, 332. 

BY GALVANISM, 332. 

,» advantages of. 

333. " 

n "biting in," 333, 



steel plates, 



ANALYTICAL INDEX. 



359 



Etching, bv galvanism, for executing 
gradations ot 
shade, 334. 
useful to ama- 
teurs 335. 
applied to etch- 
in? Daguer- 
reotypes, 336. 
Exciting fluids have various intensities, 10. 
„ have various conducting 

powers, 10. 
used in Darnell's battery, 

19- ~, 

used in Grove's battery, 22. 
used in Smee's battery. 26. 
Expense of equivalent of power, 112, 113. 
relative, of the three batteries, o2. 
" of making copper plates, 292. 
of electro-metallurgy, 112. 116. 

Faraday's voltameter, 42. 

on the chemical theory of the 

( pile, 7. 

on the poles of decomposition 

apparatus, 44. 
on the laws ot* decomposition, 49. 
" on electrolysis, 51. 

on the ions, anions, cathions, 5-J. 
" on electro-chemical decomposi- ; 
tion, 165. ! 

Ferro-sesquicyanuret of potassium, made 

by galvanism. 169, 170. 
Film of air, 109. 
Fisher. Captain, his mode of removing 

wrecks bv galvanic blasting, 339, 340. 
Formulae, Ohm' s, 11, 12. 

., results of, 12- 
" for ascertaining cost of electro- 
metallurgy, 113. 115 
of voltaic force (Smee's), 66. 
for intensity in compound bat- 
ten- (Smee's), 71. 
for amount of work (Smee's), 
74. 
Fruits, electro-coppered, 243. 

„ ' metallic moulds oi, 277. 
Fumes, nitrous, of Grove's battery delete-, 
rious, 22. ._. 

„ absence' of, in galvanic etching, 
333. 
Fusible metals, table of. 123. 

Galvanic battery. (See Battery.) 

blasting m mines and under 
* water, 339. 341. 
applied by Lieut. Gen. 

Paisley, 339. 
Capt. Fisher's mode 
of, 339. 
„ etching, 237. 

Galvanised iron, 212. . , oc 

Galvanometer, Snow Harris's, J5. 
„ magnetic, 36, 37. 

„ astatic, 39. 

„ tortion, 40. 

„ horseshoe, 40. 

(See Voltameter.) 
Gas for magnetic electricity, 84. 
Gassiot on the spark of battery, 36. 
on metallic chromes, 217. 



Geddes, Mr.. 305. ' ■ 

Gilding, electro :— preparation ot plate to 

positive r>ole, 231. 

coating of parts not to be 

gilt. 231. 
quantity of electricity re- 

quired for, 231. 
whiting used in, 232. 
colour ^of < cli reduced by, 

235. 
cooper articles, 232. jt» 
\. silver, 2.33. 

- iron and steel, 234. 

'„ copper plates, 234. 

clichees, 234. 

lead, tin, aud pewter, 234. 
Brugnatellia, 229. 
colouring of gold, 235. 
" burnishing, 236. 

water, Elkington's method of, 236. 
' solution, 236, 237. 
process, 237. 
by amalgamation. 237. 

compared with electro- 
gilding, 238. 
detrimental to 
health, 237. 

Glue used for moulding, 143. 
Glvphographv, Palmer's patent, 320. 

yy ' preparation of the plate, 

321. 
execution of the design, 

322. 
formation of electro-gly- 

phographic cnst, 323. 
formation of stereo-gly- 
phographic cast, 323. 
Gold, chemical equivalent of, 48. 

„ receives the metallic deposit, 121. 
„ reduces gold, 62. 

electro-medallions of, 256. 
„ chloride of, 180. 
,. bromide of, 181. 
' hvpo-sulphite cL 181. 
„ iodide of. 182. 
„ sulpho-cyanide, 182. 
„ reduction of:— 

from chloride, 130. 
from bromide, 181. 
from hvpo-sulphite, 
" 181. 

from iodide, 182. 
from sulpho-cyanide, 
" 1S2. 

from auro-cyanide of 

potassium, 183. 
expense of, 185. 
apparatus, 134. 
Ground for etching, 331. 

„ for gly pho ?raphy ,. o21 . 
Grove's battery, construction ot, zz. 
principle, 82. 

advantages and disadvan- 
tages of. 22. _ 
signs of action in. 34. # 
compared with Darnell's 
and Smee's, SI. S3. 
Gutta percaa for moulds, 140. 
f , troughs, 102. 



360 



ANALYTICAL INDEX. 



Gutta percha for statuettes, 247. 

,, matrices of woodcuts 

316. 

Hare's battery, 14. 
Harris's galvanometer, 33. 
Hays, Mr., electro-coppered ships, 250. 
Health, effect of metallic solutions on 
xxviii. ' 

„ effect of nitrous fumes on, 22. 
„ effect of gilding by amalgamation 
on, 237. 
Heating wires by galvanic batterv, 35 
History of electro-metallurgy, xvii. 
Horizontal decomposition apparatus, 107. 
Hydro-electricity, 80. 
Hydrogen, chemical equivalent of, 48. 

„ adhesion of, to negative plate, 
15. 

„ adhesion of, to positive plate, 

16. 
„ facilitated by amalgamation, 16, 

„ evolution of, affects the power. 
18. r ' 

„ removal of, in Daniell's bat- 
tery, 19. 21. 

„ removal of, in Grove's batterv 
21, 22. *' 

„ removal of, in Smee's battery, 

„ evolution of, in Smee'e battery 
a test of quantity, 47. 105. 
Hydnodate of zinc, 210. 
Hypo-sulphite of silver, 188. 

,t of platinum, 179. 

» of gold, 181. 



Iron, reduction of, from proto-ioduret 

214. 
T » . » expense of, 214. 

Ironing, electro, 252. 
Italian mode of making clichees, 125 

Jacobi's idea of the electrotype, xviji. 

James's electro models, 282. 

Jar, Leyden, charged by battery, 37. 

Kemp, inventor of amalgamation of zinc ot 
the battery, 16. 



Ignition of charcoal points. 37. 
Illustrated London News, 317. 
Imponderable agents, 2. 
Intaglio. (See Mould.) 
Intensity a property of the battery, 10, 11. 
effects of, 11, 12. ' 

" ^X^S' 8 batter y remarkable tor, 

„ required for electro-magnets, 40. 
» required for decomposition, 50. 
„ modes of regulating, 105. 
„ effect of, on decomposition, 155. 
„ formula for, 77. 
Iodide of gold, 182. 
„ of palladium, 186. 
„ of silver, 189. 
,, of copner, 261. 
Ions, simple and compound, 52. 

; , Faradav on, 52. 
Indium, reduction of, 186. 
- . -" ,, from chloride, 186. 

iron single-cell apparatus. 94, 95. 
„ expense of equivalent of power ob- 
tained by, 113. 
., electro-medallions, 261. 
., gilding of, 234. 
„ multiplication of articles in, 283. 
„ reduction of:— 
n „ from proto-sulphate, 

213. 
*» M from citrate, 214. 

♦» ,» from ferro-cvanite of 

potash, 214. ' 



Laws of decomposition, 49, 50. 
,, of precipitation of metals, 150. 
„ for their reduction in black powder, 

150. 
„ for their reduction in crystalline 

state, 152. 
„ for their reduction in reguline state, 
153. 
Lead, chemical equivalent of, 49. 

„ relievos in, from engraved plates. 
125. 300. r ' 

„ single-cell apparatus, 90. 
„ tree, 216. 

„ reduction of :— from acetate, 216. 
» „ from oxyde, 217. 

» „ from tris-nitrate 218. 

»> „ from plumbo-cyanide 

of potassium, 218, • 

! >■> , „ expense of, 218. 
„ reduces lead, 62. 
„ oxyde of, for metallo-chromes, 217, 
Leading, electro, 251. 
Leaves, electro-coppered, 247, 248. 
„ metallic moulds from, 277. 
Leeson's battery, 23. 
Leyden jar charged by battery, 37. 
Line engraving, 302. 
Linseed oil, preparation of plaster by, 

138. 
Local action, 6. 
„ ij overcome, 16. 

Magnetism, identical with electricity, S3. 
„ but two metals capable of, 

38. 
„ a test of quantity, 40. 

Magnetic effects of battery, 38. 41. 
„ electro machines, 81. 85. 
Magneto electricity, 84. 
Magnets, galvanometers, 38, 39. 
„ temporary, 38. 
., permanent, 38. 
„ deflection of, 38. 
„ soft iron horse-shoe, 40. 
,, electro, require intensity, 41. 
Manganese, black oxide of, in *De Luc's 
column, 14. 
„ reduction of, 223. 

Marsh's apparatus for detecting arsenic, 

Mason's decomposition apparatus, 105. 
Measures of quantity, (See Galvanometer.) 
Medals, chased, 261. 

i, ,, process of, 261. 

„ struck or coined, 262. 

» „ process of, 262. 

t, „ process at tho 

Mint, 263. 



ANALYTICAL INDEX. 



361 



Medals, multiplication of, 253. 
„ moulds from, 121. 254. 
„ best suited for multiplication. 
2G8. 
Medallions, electro, of gold, 256. 
„ „ of silver, 256. 

„ „ of platinum, 257. 

„ „ of palladium, 257. 

„ „ of copper, 258. 

., ,, of zinc, 261. 

„ „ of iron, 261. 

„ of hard copper, 241. 
„ „ thickness of, 260. 

„ „ removal of, from 

moulds, 260. 
„ „ gilding of, 261. 

„ „ battery process, 258. 

259. 
., „ other processes, 259. 

„ „ with perfect rim, 267. 

„ „ with obverse and re- 

verse, 268. 
Mercury, used for amalgamating zinc of 
batteries, 16. 
„ to be preserved after reduction 

of zinc, 29S. 
,, gilding by, 237. 
„ blcyanide of, 175. 
MetaL tvpe, composition of, 122, 123. 

„ fusible, 123. 
Metals, relative conducting powers of, 3. 
„ electro-negative, 4. 
„ electro-positive, 4. 
„ become infilmed with air, 18. 
„ reduction of, various forms for, 

147. 
„ „ laws regarding, 150. 

,, „ in black powder, 150. 

„ „ in crystalline state, 

152. 
„ „ in reguline state, 153. 

„ effects of intensity on, 154, 155. 
„ effects of quantity on, 156. 
„ reduce like metals, 60. 
Metallic solutions, variations in strength 

of, 161, 162. 
Metallic salts, formation of, 167. 
Metallo-chromes, 217. 

Metallo-cyanides, electro-chemical de- 
compositions, 169. 
,. preparation of, 171. 

Mezzotinto engravings,. 303. 
Moulds in silver leaf, 121. 
„ in alloys. 122. 
„ in fusible metals, 122. 
,, clichees, 124. 
,, by the press. 125. 
„ in lead from engraved plates, 125. 

300, 
,. by stereotyping, 126. 
„ in sealing-wax, 126. 
„ in whitewax. 128. 
„ in white wax, from plaster casts, 

129. 
„ in stearine, 130. 
„ in spermaceti, 130. 
., in bees' -wax and rosin, 131. 
„ in paper, 131. 
,, in plaster of Paris, 1S2. 134. 
„ in sulphur, 141. 
y in gutta percha, 140- 



Moulds in bread, 143. 

„ in glue and whiting, 143. 

„ metallic coatings for, 144. 

„ from medals and coins, 121. 254, 
255. 

„ from monumental brasses, 274. 

„ from embossed surfaces, 276. 

„ from fruit leaves, &c, 277. 

,, from engraved plates, 301. 
Muriate of copper, 200. 

„ of tin, 215. 
Murray first applied black-lead to non- 
conductors, 22. 

Needle, astatic, 39. 
Negative-electro metal, 4. 

„ „ surface of, 7, 

„ „ cleanness import- 

ant, 15. 
„ ,, adhesion of hy- 

drogen to, 15, 
of Darnell's bat- 



ten* 19. 



bat- 



„ „ of Crrove'8 

tery, 22. 
„ „ of Smee's battery, 

24. 26. 
„ pole, 44. 
Newton's, Sir I., fusible metal, 123. 
Nickel, reduction of: — 

„ „ from nitrate, 193. 

„ „ from sulphate, 193. 

„ „ from acetate, 193. 

„ „ from chloride, 194. 

„ ., expense of, 194. 

Nickeling, electro, 240. 
Nitrate of copper, 199. 
„ of silver, 187. 
of nickel, 193. 
„ of palladium, 185. 
| Nitric acid used in etching, 231. 
Non-conducting substances :— 

„ first class, 

126. 
M „ second class, 

„ „ third class, 

141. 
„ „ metallic 

coatings 
for, 143. 

145. 
Numismatist, value of electro-metallurgy 
to, 253, 

; Ohm's formula for the galvanic current, 
11. 12. 
,, results of, 12. 

i Oil, linseed, preparation of plaster by, 
138. 

,, nut, preparation of plaster by, 139. 
Ordnance map office, 530. 
Osmium, reduction of, from oxyde, 187. 
: Oxygen, chemical equivalent, 48. 
! Oxydes, compounds of, with alkalies, 168. 

,, „ with salts, 168 

! Oxyde of copper, 201. 
! Oxalion, 56. 
; Oxycarbion, 56. 
I Oxynitrion, 56. 
Oxysulphion, 56, 






362 



ANALYTICAL INDEX. 



Palladio cyanide of potassium, 186. 
Palladium, reduction of:— 

w u from nitrate, 185. 

» m from ammonio- 

nitrate, 185. 
» m from palladio- 

cyanide of po- 
tassium, 186. 
?> , v expense of, 186. 

„ electro-medallions of, 257. 
Palladiatmg, electro, 241. 
Palmer's patent glyphography, 320. 

„ electrotmt, 325. 

Paper, absorption of, prevented, 131. 

„ metallic moulds from, 276. 
Patents :— 

laws regarding, 349, 351, 
Baggs, I., 353. 
Barratt, O., 353. 
Elkington's, 352, 353. 
Jones's, A., 353. 
Leeson's, H. B., 353. 
Lockett's, I.. 352 
Mabley's, W. T., 352, 
Palmer's, E., 353. 
Shore's, I., 352. 
Spencer's, T., 352. 
Talbot, W. H. F., 353. 



353. 



metallic salts, 



Tuck's, E., 354. 
Woolrich, J. S., 
Perkins's apparatus, 312, 
Phosphorus reduces the 

144. 

Plaster of Paris, composition of, 133. 
casts of, 134. 
preparation of casts, 134. 

138. 
apparatus, 93. 
list of substances ren- 
dering it non-absorb- 
ent, 139. 
medallions, copied, 255. 
intaglios in, 255. 
Plates of battery, 4. 11. 

„ copper. (See Copper.) 

„ reduction of platinum : 

» » from chloride, 176. 

»> »> in black powder, 

176. 
v ?» in reguline state, 

177. 
» »» from hyposulphite, 

179. 
„. ». , jy expense of, 179. 

Plating by ordinary mode, 243. 
„ electro, 241. 

„ solution, 241. 

„ precipitated silver, 241. 

„ positive pole, 241. 

^, . ii on copper, 243. 

Plating, electro, on lead, 242. 

m on non-conductors, 243. 

■ . m advantages of, 244. 

Platinum, negative metal on Grove's bat* 
tery, 22. 
„ for poles of Faraday's voltame- 
ter, 42. 
„ electro-medallions, 257. 
„ solution of, for bronzing, 207. 
Platmating, electro, 238. 

n v application of, 240 



Platinizing, electro, 239. 

» ., negative metal, for 

Smee's battery, 24, 

Platinized silver for Smee's battery, 25, 

Platinode, 44. 

Plumbago. (See Black-lead.) 

Poles of decomposition apparatus, 44. 

„ synonymous with electrodes, 44. 

„ Faraday on the, 44. 
Porous tubes in Daniell's battery, 19, 20. 
„ in single-cell apparatus, 88, 

„ substances best adapted for, 

87. 89. 
Positive metal, 4. 

„ local action on, 6. 16. 

„ size of, 7. 

„ distance from negative, 8. 

„ adhesion of hydrogen to, 

16. e 

« amalgamation of, 16, 17. 

„ pole synonymous with 

_ anode or zincode, 44. 

Potash, dichromate of, in Leeson's bat- 
tery, 23. 
Potassium, aurocyanide of, 183. 

,, palladio^cyanide of, 186. 

,, sulphuret of, for bronzing, 

208. 
Potteries, use of engraved plates in, 303. 
,, application of electrotype to. 
304. ' 

Poulton's Barton's button 280. 
Powder, black, of metals, 148. 

it » law for reducing, 150, 151. 

u „ obtained with given solu- 

tion, negative plate, qr 
- battery, 158. 

Power of battery, 10. 

„ equivalent of, 48, 49. 
Power from hydro-electricity, 80. 
„ animal electricity, 81. 

„ . lightning electricity, 81. 
Precipitating trough, materials adapted 
for, 99. 101. 
v » compound, 99. 

?> ,» earthenware, 101. 

n •, wooden, 101. 

h 7) leaden, 101. 

i> „ gutta p'ercha. 102. 

»i „ Terry's form, 102. 

h i, for making elec- 

tro-copper me» 
dallions, 258. 
ii m for multiplying 

copper-plates, 
294. 
>♦ |, horizontal Gom? 

pared with ver- 
t, . , , . tical, 106. 

Pnng's etching, 337. 
Printed pictures, 319. 
Printing, ordinary method, 289. 
„ stereotype, 290, 
„ electrotype, 290. 
„ from wood-cuts or surface, 314, 
„ calico, 304. 
„ anastatic, 291. 
Punch, frontispiece of, 317 



ANALYTICAL INDEX. 



3f,3 



Quantity of electricity influenced by size 
of negative plate, 
7. 

„ „ varies with strength 

of exciting fluid, 
8. 

„ „ measured by volta- 

meter, 46. 

,. „ mode of regulating, 

• 105, 162. 

„ „ effects of, in reduc- 

tion of medals, 
156. 

Reduction of alloys, 225. 
„ antimony, 218. 

„ arsenic, 220. 

„ bismuth, 219. 

„ cadmium, 212. 

„ cobalt, 223. 

„ copper, 194. 

gold, 180. 
„ iridium, 186. 

L iron, 213. 

Z lead, 176, 216. 

„ manganese, 223, 

„ nickel, 193. 

„ osmium, 187. 

„ palladium, 185. 

„ platinum, 176. 

„ rhodium, 186. 

,, silver, 187. 

„ tin, 215. 

„ tungsten, 223. 

„ uranium, 219. 

„ zinc, 208. 

Reguhne state, reduction of metals in, 148. 
„ with any given solution, 

negative plate or battery, 
159. 
Rhodium, reduction of, from sodio-muriate, 
. 186. 

Rose's fusible irietal, 123. 
Rosin and bees' -wax, moulds m, 131, 225. 
preparation of plas- 
ter by, 137. 
„ and turpentine, preparation of plas- 
ter by, 137, 
„ and grease, preparation of plaster 
by, 138. 
Russell's process, 308. 

Salts, metallic, formation of, 167. 

by galvan- 
ism, 167. 
Sculpture, application of electro-metallur- 
gy to, 279. , 
casting, present method of, 279. 
casting, by electro-metallurgy, 

279. 
casting, from large designs, 279. 
expense, 280. _ 

texture of reduced metal for 
casting,, 280. 
Sealing-wax, composition of, 126.. 

" impressions, 127, 255. 
Seals, process for copying, 269. _ 
Secondary effects of decomposition, 53, 54* 
Ships, electro-coppered, 250. 

„ copper 6heathing preserved, 5. 
Shock ofgalvanic battery, 37. 

t, electro-magnetic apparatus, 82, 



Silliman's copies of pearl, 281. 
Silver, chemical equivalent, 49. 
„ used to receive the metallic deposit, 

121. 
„ reduction of :— 
„ „ from acetate, 188. 

„ j, from argento-cyanide 

of potassium, 190. 
„ „ from ammonio-nitrate, 

188. 
„ „ from ammonio-chlo- 

ride, 188. 
j, „ from ammonio-carbo* 

nate, 189. 
„ „ from hypo-sulphite, 

188. 
„ „ from iodide, 189. 

„ „ from nitrate, 187. 

fi „ from potasso-tartrate, 

189. 
ti j, from sulpho-cvanide, 

189. 
„ „ expense of. 192. 

„ electro-medallions in, 256. 
„ quality of reduced metal, 257. 
„ on the multiplication of articles in, 
285. 
Silvering, electro. (See Plating.) 
Single-cell apparatus, 87. 

„ diaphragms for, 87, 

89. 
„ porous tubes for, 88. 

„ various forms of, 92, 

93. 
,, zinc for positive 

pole, 93. 
„ iron for positive 

pole, 94, 95. 
„ lead for positive 

pole, 96. 
„ tin for positive pole, 97. 

„ union with battery apparatus, 

102, 103. 
Smee's battery, principle of, 24. 

„ platinizing of negative 

metal, 24, 25. 
„ platinized silver, best for 

negative metal, 25. 
„ exciting fluid of, 26. 

„ various arrangement of, 

26, 29. 
„ form best suited for electro- 

metallurgist, 27. 
„ odds and ends' battery, 28. 

„ construction and use, 28. 

,; advantages and disadvan- 

tages of. 29. 
„ exciting fluid, strength of, 

29. 
compared with Daniell's 
and Grove's, 31, 32. 
„ voltameter, 4G. 

„ formulae, '64;. • • 

Sodio-muriate' of rhodium, 186. 
Spark of battery, 36. 

Gassiot on, 36. 
„ Crosee on, 38. 

Specula, multiplication of, 285. 

tpelter, cheaper than rolled zinc, 113. 
PQncer, his idea of the electrotype, e 
Spermaceti, moulds in, ISO. 



364 



ANALYTICAL 1XDEX. 




Spermaceti renders plaster non-absorbent, 

Stearine, manufacture of, ISO. 

,, moulds in, 130. 

V , Preparation of plaster by, 135, 136 
Steel plates, multiplication of:— ' 

is » by electro- 

** »» metallurgy, 

310. 6,y ' 

•* & by Perkins' 

process, 312. 

" 'a by stereo- 

Stereotype printing, 289. tyPG ' 313 * 

Stereotyping, process of, 94. 
Stereo-glyphography, 323. 
" Stopping out" in etching, 331. 
bulphate of zinc in exhausted batterv. Its 
use, 298. 

U of zinc, 208. 

of silver, 188. 

„ of nickel, 193. 

„ of copper, 195, 196. 

„ of cadmium, 212. 
Sulpho-cyanide of copper, 202. 
Sulpho-vinion, 56. 
Sulphur, casts in, from plaster, 141. 
c , . " , _ n sulphur, 142. 

bulphuret of potassium, for bronzing, 208; 

Table of chemical equivalents, 48, 49. 
„ of fusible metals and alloys, 123. 
„ bf cost of equivalent power under 

^various circumstances, 115. 
„ of expense of reduction of copper 

by various methods, 115. 
„ of substances which render oxvdes 

soluble, 166. 

,* of substances for making moulds,119< 

„ of principal modes of making- 

moulds, 120. s 

Tallow renders plaster non-absorbent, 

137. 
Theory, chemical, 7. 

„ contact, 7. 
»«,.", of the reduction of alloys, 224. 
" Timbs' Year-Book of Facts," 281. 
Times machine, 318. 

newspaper, 318. 
reduction of:— 

n from muriate, 215. 

„ from sulphate, 215. 

„ from acetate, 215. 

„ from oxalate, 215. 

from other salts, 216. 
expense of, 216. 
positive pole in single- 
cell apparatus, 97. 
expense of equivalent of 
power obtained bv, 
113. • y ' 



Tin, 



ft 

■ 

Tinning, electro, 251. 
Tortion galvanometers, 40. 
"'rough, precipitating, 99. 101. 
iten, reduction of, 223. 



Troug 
Tung* 



Turpentine and rosin render plaster nori- 

absorbent, 137. F non 

Type, metal, 122, 123. 

„ manufacture of, 122. 

, , multiplication of :— 

" n by electrotype, 290. 

" v by stereotype, 290> 

Uranium, reduction of, 219. 
V-shaped tube, 42. 

Varnishes render plaster non-absorbent, 
138. 

ren £f r paper non-absorbent, 
132. 

Vegetables, electro-coppering of, 247 248 

Tr , .m , metallic moulds from, 277 

Voltaic battery, 2. (See Battery.) 

„ current, proximate cause of, 6. 

»> » theory of, 59. 

„ equivalents, 48, 49. 

„ circles, curious instances, 67— 69; 
Voltameter, Faraday's, 42. 

„ a test of quantity, 46. 
„ Smee's battery, 47. 

Water, an exciting fluid, its use, 9. 

" S^&ng, Elkington's mode of, 236. 
237. * 

Wax, white moulds in, 128. 255. 

„ preparation of plaster bv 
137. 
Whiting used in electro-gilding, 238. 
Wires, heated by battery, 35. 

„ thin, bad conductors, 11. 
W ood-cuts, durability of. 314. 
„ printing from, 314. 

j, multiplication of, 315. 

„ clichees from, 315. 

„ electrotypes from, 316. 

Yalland, Captain, 305. 

Zinc, chemical equivalent, 49. 

„ amalgamation of, with mercury. 16. 

„ positive to nearly all metals, 4. 

>, positive metal in single-cell appara- 
tus, 93. ^ 

„ reduction of :— 

>j it on negative plates of 

battery, 211. 

» », by zinc, 61. 

» » from sulphate, 208. 

t't » from ammonio-sulphate, 

209. 

» »> from chloride, 209. 

»• m from acetate, 210. 

» » from hydriodate, 210. 

>j », from other salts, 211. 

» , ?> expense. 212. 

„ electro-medallions, 261. 
Zinced iron, 122. 
Zincing-electro, 251. 

Zincode, synonymous with anode, elec- 
trodes, 44. 



KD-83 



THE END- 






^0< 







r ** 




«.«?. 



o • t 



<W .•»'•- \/ :m£: %.J ' 




* I "» 









• I 



« * 







•^ 



.** 




^1 






* ^ 









r v 












4C ^ ^o *9^ 








,0 






DOBBS BROS. 

LIBRARY BINDING 4 V^ 




o v 



< • o 



ST. AUGUSTINE t o 
^^32084 









■ 



LIBRARY OF CONGRESS 




■ 



014 633 322 9 






I 



mt 



I 



